Pump and Motor
In electrical terms, a motor is a machine for
converting electrical energy into mechanical energy.
You need to be familiar with the terminology
used in context with motors and pumps:
||The air space
between two magnetically related or electrically related parts
- for example, the space between poles of a magnet or the
poles of an electric motor.
current that alternates, flowing first with a positive
polarity, followed by a negative polarity.
device consisting of two or more conducting plates separated
from one another by insulating material and used for storing
an electrical charge.
material that separates and insulates the conducting plates in
a capacitor. It can be a gas, liquid, plastic, glass, paper -
or a combination.
||The failure of
an insulating material to separate electrical charges.
Breakdown occurs when the insulating material changes and
conducts the electrical charge between plates.
the number of times alternated current changes direction
during one second. Frequency is measured in hertz (cycles per
||A unit of
measurement of frequency. Hertz indicates "cycles per
second" of alternating current.
unit of measure foi- power, this indicates the result of force
multiplied by distance multiplied by time. One horsepower (hp)
equals 746 watts, or 33,000 foot pounds per minute or 550 foot
pounds per second.
||A test of an
electric motor in which the shaft is prevented from turning
while power is applied. It can, for example, be used to
determine fixed and variable losses in a motor.
Electrical Manufacturers Association.
motor at full speed with no load to determine rotational power
part of an electric rotating machine. In a motor it is
connected to and turns the drive shaft. In an alternator or
generator it is turned to produce electricity by cutting
magnetic lines of force.
||A measure of the
reserve margin built into a motor. Motors rated more than 1.0
SF have more than normal margin and are used where unusual
conditions such as occasional high or low voltage, momentary
overloads and so forth are likely to occur.
||Having only one
alternating current or voltage in a circuit.
part of a motor that contains the laminated steel core with
the winding; this is where the rotor revolves.
||A force that
produces a rotating or twisting action.
switch used in applications such as power switches, light
dimmers and motor controls.
pressure; the force that causes current in an electrical
||A unit of
electrical power representing the power developed in a circuit
by a current of one ampere when the voltage drop is one volt.
for measuring electrical power.
current split-phase induction motor that has a capacitor
connected in series with an auxiliary winding for starting.
The auxiliary circuit disconnects when the motor is up to
speed. This motor requires an internal starting switch and
split capacitor motor
electric motor that uses a phase winding in conjunction with
the main winding. The phase winding is controlled by a
capacitor that stays in the circuit at all times and is rated
for continuous running. The capacitor improves starting and
running power factors. This motor does not require either an
internal starting switch or a governor.
motor (also known as a resistance start motor)
induction motor that has an auxiliary winding connected in
parallel with the main winding. The auxiliary winding's
magnetic position is not the same as the main winding, so it
can produce the required rotating magnetic field needed for
starting. This motor requires an internal starting switch and
||A motor that
operates from a three-phase power source. In three-phase
power, three voltages are produced that are 120 electrical
degrees apart in time. This motor has no internal starting
motor that uses one capacitor for starting and one for
running. The starting capacitor is in parallel with the
running capacitor as the motor is starting; at 75 percent of
speed, the starting capacitor is cut out of the circuit. This
type of motor is sometimes called capacitor start/capacitor
run and requires an internal starting switch and governor.
Pool and spa pumps are classified as
centrifugal pumps. That is, the centrifugal force that is created by
spinning the water, will force the water downwards and if there is
an opening or a hole, this water will get pushed forward through the
The pump operates the same way. The impeller
in the pump spins, shooting water out of it. As the water escapes, a
vacuum is created that demands more water to equalize this force.
Water is pulled from the pool or spa and sent on its way through the
circulation plumbing. The hole size determines the amount of water
and how fast it can escape. Also the various designs of impellers,
diffusers, and volutes determine the same features in a pool pump,
which is discussed later.
Pumps used for pools are self-priming, that
is, they expel the air inside upon start-up, creating a vacuum that
starts suction. Once water is flowing through the pump, if you close
a valve on the outflow side of the pump, restricting all flow,
maximum possible pressure is created. However, there is no
destructive force created, the impeller simply spins in the liquid
Pot And Basket
The plumbing runs to the inlet port of the
pump, from the pool or spa main drain and skimmer. The inlet is
usually female threaded for easy plumbing.
Water flows into a chamber, called the
strainer pot or hair and lint trap. This chamber holds a basket that
permits water to pass but retains the debris. Generally the basket
is 4 to 6 inches in diameter and 5 to 9 inches deep, and is made of
plastic mesh. In some pumps the strainer pot bolts to the volute
with a gasket to prevent leaks, while in yet others it is molded
together with the volute as one piece. In bathtub spas or booster
pumps, there is no strainer pot and basket at all since debris is
not a problem.
There is an access provided to clean out the
strainer basket, and also have cover that are usually made of
transparent plastic and can easily be attached with a nut and a
bolt. The strainer cover has an O-ring between the lip of the
strainer pot and itself. This prevents any leakage due to suction.
Also the pot has a small threaded plug that screws into the bottom.
This plug is designed to allow complete drainage of the pot when
winterizing the pump. It is made of a weaker material than the pot
on metal pots, for example, the plug is made of plastic, soft lead,
or brass. If the water in the pot freezes, this sacrificial plug
pops out as the freezing water expands, relieving the pressure in
The volute, is the chamber in which the
impeller spins, that forces water out of the pump and into the
plumbing that takes the water to the filter. The outlet port is
usually female threaded for easy plumbing. The movement of the
impeller sucks the water from the pool through the strainer pot. The
resulting vacuum in the pot is compensated for by water filling the
void. The rushing water is contained by the volute which directs it
out of the pump. Therefore the pot can be considered a vacuum
chamber and the volute a pressure chamber.
The impeller by itself cannot create a strong
vacuum by itself to make the water flow begin. The area immediately
around the impeller must be limited to eliminate air and help start
the water flow. A diffuser and/or closed-face impeller help this
process, but in many pump designs, the volute serves this purpose.
In some designs, the inside of the volute is ribbed to improve the
The impeller is a ribbed disk that spins
inside the volute. The disk is called a shroud and the curved ribs
are called vanes. Water entering the center of the impeller, is
forced to the outside edge of the disk by the vanes. As the water
moves to the edge, there is a resulting drop in pressure at the
center, creating a vacuum that is the suction of the pump. The
amount of suction is determined by the design of the impeller and
pump components and the strength of the motor that spins the
There are two types of impellers, closed-face
and semi-open-face. In the closed-face impeller, the vanes of the
impeller are covered in both front and back. Water flows into the
hole in the center and is forced out at the end of each vane along
the edge of the impeller. This type of impeller is very efficient in
moving water and a diffuser is added to the design to slow the speed
of the water before it leaves the volute. This design does not take
into consideration the debris that might escape the skimmer and
strainer basket and into the impellers. This led to the new design,
the semi-open-face design allowing small debris to pass by actually
pulverizing it. Diatomaceous earth is the chief cause of clogging in
Impellers are rated by horsepower to match the
motor horsepower that is used. This, in turn, determines the
horsepower rating of the pump or pump and motor you have. Usually
the motor is of higher horse power than the impeller.
Plate And Adapter Bracket
The volute is divided into two sections, the
rounded volute and the seal plate. This allows an access to the
impeller. The seal plate is joined to the volute with a clamp or
with bolts. An O-ring between them makes this joint watertight. The
motor is bolted directly onto this type of seal plate. In other
designs, the seal plate is molded together with an adapter bracket
that supports the motor and bolts to the volute, with a paper or
rubber gasket between them to create a watertight joint.
In both cases, the shaft of the motor passes
through a hole in the center of the seal plate and the impeller is
attached, threaded onto the shaft. The bracket allows access to the
shaft extender for adjusting the clearance between the impeller and
volute. The pump design of closed face needs no such adjustment, so
the shaft need not be exposed.
And Shaft Extender
The shaft of the motor is the part that turns
the impeller, creating water flow. The impeller needs to be adjusted
in relation to the volute, so a shaft extender has been created. The
extender, made of brass or bronze, slides over the motor shaft and
is secured by three allen-head setscrews. The male threaded end of
the shaft extender then fits through the seal plate and the impeller
is screwed into place.
The extender is round with a flat area on two
sides to prevent the extender from spinning when performing
maintenance. Some designs require an O-ring near the threads of the
extender to ensure a watertight seal. While other designs rely only
on the pump seal.
The shaft should never be in contact with
electric current, so most motor shafts today are designed with a
special internal sleeve to insulate the electricity in the motor
from the water in the pump.
The seal allows the shaft to turn freely while
keeping the water from leaking out of the pump. If the shaft passed
through the large hole of the seal plate without some kind of
sealing, the pump would leak water and if the hole was made small
and tight, perhaps of tight-fitting rubber, the high-speed spinning
of the shaft would create friction and burn up the components.
The seal is in two parts. One half of the seal
is composed of a rubber gasket or O-ring. This is fitted around a
ceramic ring and fits into a groove in the back of the impeller. The
ceramic ring can withstand high temperature caused by friction. The
other half of the seal is made of a metal bushing and a spring. This
fits into a groove in the seal plate. The end of the spring that
faces the ceramic ring is covered with a heat-resistant graphite.
Since the spring exerts pressure on both the sides it makes the
whole seal water tight there by preventing the water from leaking
out of the pump.
As the shaft turns, these two halves spin
against each other but do not burn up because their materials are
heat-resistant and the entire seal is cooled by the water around it.
Therefore, if the pump is allowed to run dry, the seal is the first
component to overheat and fail. Pumps are not designed to run
without water for more than a few minutes while priming.
Motors are rated by horsepower. The most
common ratings for pool and spa motors range from 0.5 to 2.0
horsepower. Electricity flows through the motor windings, which are
thin strands of coiled copper or aluminum wire. The windings
magnetize the iron stator. Using this concept, the rotor spins,
turning the shaft. The shaft rides on ball bearings at each end. A
built-in fan cools the windings because some of the electrical
energy is lost as heat. The caps on each end of the motor housing
are called end bells. A starting switch is mounted on one end with a
small removable panel for connection and maintenance access.
The thermal overload protector, a heat
sensitive switch that is like a circuit breaker, is mounted on the
panel. If the internal temperature gets too hot, it shuts off the
flow of electricity to the motor to prevent greater damage. As this
protector cools, it automatically restarts the motor, but if the
unit overheats again, it will continue to cycle on and off until the
problem is solved or the protector burns out.
The capacitor of the motor is located on top
of the motor housing in a separate box or housing. The capacitor,
has a capacity to store an electrical charge and when discharged it
gives the motor enough of a jolt to start. This way the capacitor
can impart enough energy to start the motor and then run on a lower
amount of electricity. A motor needs more electricity to start than
to keep it going. Without the capacitor, the motor would need to be
served by very heavy wiring and high-amp circuit breakers to carry
the starting amps.
Some motors are designed to operate at two
speeds, the normal rotation speed is 3450 revolutions per minute
(rpm) and the low speed is 1750 rpm, depending on the need for
circulation and heating or for jet actions (in spa).
The three main types of motors that you find
in pool and spa are:
When the start up power requirements are low,
the motor is usually 1/4-horse power or less. It also does not
require any capacitor.
Capacitor start, induction run (CSI)
This is the most commonly used motor in the
pool business. This motor uses a capacitor and starting windings to
start up, then these are shut down and a running winding takes over.
As noted previously, the capacitor and start-up windings allow
faster, stronger torque to overcome the initial resistance of the
impeller against standing water, then when the water is moving and
less power is needed to keep it moving, the system shuts off and the
lighter running winding takes over.
Capacitor start, capacitor run (CSR)
This is the concept of the energy efficient
motor. The difference between a CSR and CSI motor is that the CSR
motor employs a capacitor on the running windings as well. This
smoothes out the variations in the alternating current (ac) power
that helps reduce heat loss in the winding. In short, CSR motors are
more efficient but cost more because of the added parts. These
motors are also called switch-less, because on some designs the run
capacitor makes a start switch unnecessary. These are the most
energy efficient motors when they have heavier wire in the windings
to lower the electricity wasted from heat loss. A good way to
compare energy efficiency between two motors is to compare the
gallons pumped to kilowatts used. The higher the resulting number,
the more efficient is the pump and motor. Kilowattage is determined
by multiplying amps by voltage.
Motors are most commonly designed to work on
110 or 220 volts. Higher horsepower motors might run on three-phase
current. So it is best to get the work done by a certified
The variety of the motor are designed for pool
pumps. The motor must be compatible to the pump design. The motor
face could be C-frame or square-flange type, so check for the
correct fit and compatibility with the pump.
The service factor of a motor is a multiplier
number. When this number is multiplied with the horsepower rating of
the motor, you get the real horsepower at which the motor is
designed to operate on a continuous basis. As an example, a motor
rated at 1 hp with a service factor of 1.5 can actually safely run a
1.5-hp pump (1.0 x 1.5 = 1.5 hp).
Here is the detail that you get from the
nameplate on any motor:
A diagram showing how to wire the starting
switch plate for 110 or 220 volt supply. If this diagram is not on
the outside of the motor, remove the small access door in the end
bell and it should be printed on a sticker in there. These stickers
frequently come off as the motor gets older, so if no diagram is
available, refer to the manufacturer's guidebook available at your
The nameplate also tells you of the maximum
load or amperage. It might say "10.5/5.2." This means the
start-up draw is 10.5 amps, and the normal running draw is 5.2 amps.
Some times the manufacturers also mention the amps required to power
the nominal horsepower as well.
The nameplate also lists the electrical
phasing and cycle frequency in hertz. Alternating current in the
United States runs on 60 hertz. In Europe it is 50 hertz, and that's
why you can't use some appliances from one country in another, even
with a voltage converter.
Manufacturer and date
The manufacturer's name appears on the rating
plate, along with the model and serial numbers, and includes the
day, month, and year the motor was built.
The relative strength of the motor is
expressed in horsepower and corresponds to the specifications of the
pump that is to be driven by the motor.
A diagram of the wiring connections is printed
on the name-plate. There will also be a few words about mounting,
such as "mount horizontally" or "mount with vents
Pool and spa motors are designed for
continuous duty, meaning they can run 24 hours a day for their
entire service life without stopping. The nameplate shows this by
the rating "Continuous Duty." The horsepower, service
factor, rpm, and frame style of the housing are listed. If the motor
has a thermal overload protector, the nameplate will indicate it.
Other information is also shown on the
nameplate, such as the starting method (C means capacitor for
example), the insulation category, a rating of UL (Underwriter's
Laboratory) or CSA (Canadian Standards Association) approval, and
ambient (surrounding) temperature requirements.
To find the correct horsepower of the motor or
the pump, that is required for the job, it is best to consider the
needs of the pool and spa, hydraulics involved and the horsepower of
the equipment. This gives you the right size of the unit that needs
to be installed.
The study of water flow and the factors
affecting that flow is Hydraulics. It is important to understand
because its principles affect plumbing and equipment sizing choices
for there are so many factors involved.
Terms commonly used
Head and Flow rate Head is the
resistance of water flow through plumbing and equipment expressed in
feet. The lower, the better. Flow rate is the volume of water moved
in a given period of time.
As the length of the plumbing pipe increases
the resistance will bring down the flow rate.The additional
resistance (head) of that added pipe means that the pump cannot push
the water as fast. This loss of flow, as head increases, is called
head loss, a somewhat deceptive term because it is actually flow
that is lost. The term actually means flow loss caused by head
increase. If you continue to increase the head (resistance) by
adding more vertical pipe, the flow rate will continue to decrease
until at last, no water comes out at all. This pump can now be
charted on a graph, allowing you to study its performance
characteristics. On the left side of the graph is the possible feet
of head, from 0 to 10 feet. On the bottom is the possible flow rate,
from 0 to 10 gpm. By finding where the head and flow rates
intersect, you can create a pump curve for your pump.
Because you generally have no way to measure
these factors, the manufacturer provides a pump curve for each pump.
If you know the amount of head (resistance) in your pool or spa
system and you know the desired flow rate, then you can determine
which pump will satisfy those needs by referring to the
manufacturer's pump curves.
Pumps are designated low, medium, high, or
ultra-high head. The higher the head designation, the less strain is
placed on the pump and motor components: Low head-suck well; push
poorly; Medium head-suck well; push well; High head-suck poorly;
push well (most common in pools and spas); Ultra-high head-suck
poorly; push well (pool sweeps).
One factor affecting which type a particular
pump will be is its impeller. Thin vents on the face (closed or
semi-open) result in greater push but poor suck; in other words,
poor self-priming capabilities but good circulating flows.
Suction head, so far discussed, is the
head created by adding resistance to the outflow side of the pump.
By restricting the intake or requiring the pump to lift water from a
source below it, you also create head. This is called suction head,
sometimes called vertical feet of water. Each foot on the suction
side equals a similar foot on the discharge side, called discharge
head. The only thing to remember here is that head (resistance) is
created on both sides and must be calculated when determining pump
Dynamic and static head Up to now the
static head or the head created by the weight of standing (static)
water is described. This is only a small portion of the total head
in the system. The rest is created by the friction of water flowing
through the entire system, called dynamic (moving) head. The
diameter of the pipe and the speed of the water determines how much
resistance is created by friction. Further friction is created when
water must go through or around other obstacles, such as through the
filter, heater, solar panels, and plumbing fittings for every
plumbing elbow or bend creates head too.
Cavitation refers to the vacuum created
when the outflow capacity of a pump exceeds the suction intake. This
happens, for example, when a pump is oversized for the suction line
or when the distance from the body of water is too far. The result
is bubbling and vibration.
Total dynamic head (TDH) is the total
of plumbing and equipment head for the entire system. Vacuum head
(suction) plus pressure head (discharge) equals total dynamic head.
Shut-off head The amount of head at
which the pump can no longer circulate water. It is 0 gpm.
Calculations Here are a few general
numbers to use in your calculations.
Pipefittings, To make it easier to calculate
head in your plumbing system, it is measured for every 100 feet of
pipe or the equivalent. Plumbing connections, fittings, and valves
have different amounts of resistance than straight pipe, so these
must first be converted to the equivalent length of straight pipe.
Unions and straight connectors act like additional lengths of
straight pipe, so no special calculations are needed. Going around
corners is what creates head. Here are the values for the most
common PVC fittings you will use:
- 1/2-inch x 90-degree elbow = 7.5 feet of
straight 1/2-inch pipe
- 2-inch x 90-degree elbow = 8.6 feet of
straight 2-inch pipe
- 1/2-inch x 45-degree elbow = 2.2 feet of
straight 1/2-inch pipe
- 2-inch x 45-degree elbow = 2.8 feet of
straight 2-inch pipe
It is interesting to see that three times as
much resistance is created when a 90-degree fitting is used instead
of a 45. That is particularly significant, because there are times
when you have a choice between using two 45-degree fittings in a job
rather than one 90. The combination of two 45-degree fittings
creates less resistance than one 90. Also note that in a T fitting,
the turn around its 90-degree bend is sharper than the more gradual
sweep through 90 degrees created by a typical 90 fitting. Thus, more
resistance is created in a T fitting, even though the water is being
bent 90 degrees in either case.
Filters create 5 to 7 feet of head. The
manufacturer will tell you in the literature that accompanies the
product how many feet of head the unit creates. You can also measure
the amount by placing a pressure gauge on the pipe leading into the
filter and one on the pipe going out. The difference, measured in
pounds per square inch (psi), tells you the feet of head. As dirt
builds up in a filter, however, head increases. A clean filter will
have no more than 3 psi difference between the input pressure and
the output pressure. Since 1 psi equals 2.31 feet of head, a new,
clean filter should add no more than 6.9 feet of head.
Manufacturers recommend cleaning a filter when
the operating pressure (as read on the pressure gauge, expressed in
psi) builds up to more than 10 psi over clean operating pressure.
Since 10 psi equals 23.1 feet of head, you can see that the
resistance caused by dirt added to the normal amount of head for the
filter itself can total over 30 feet of head for this component
alone. This is another factor why providing a slightly larger
horsepower pump than required on a system is a good idea.
Heaters create 8 to 15 feet of head. Like
filters, the manufacturer will tell you in the literature that comes
with the unit what the head loss is for the unit at a given flow
rate. Also like filters, as scale builds up in the heat exchanger,
more friction is created and therefore more head. This is another
good reason to beef up your pump when doing the sizing calculations
for an installation.
Poolside hardware Main drain covers,
skimmers, and return outlets all add head. To know exactly how much,
you must refer to each manufacturer's specifications. A general rule
of thumb is to add 5 feet of head to allow for the total of such
components in your system.
Pumps Pumps also create head, but the
manufacturer's charts allow for this, so your calculations need not
consider it. When you look at the TDH for the system on the pump
curve, the pump head loss is already figured in the performance
Turnover rate The turnover rate of a
body of water is how long it takes to run all the water through the
system. It is desirable for the water to completely circulate
through the filter one to two times per day, but local codes
generally require a specific time period. In Los Angeles, for
example, it is 9 Pools must turn over in 6 hours, Spas must turn
over in 1/2hour, and Wading pools must turn over in 1 hour.
Various components offer more or less
resistance at different speeds expressed in gallons per minute. To
calculate the TDH of a system, you must know that speed. To decide
what speed is needed (and therefore what size pump is needed to
deliver that speed in your system) you must establish a turnover
Let's say if you've calculated the volume of
water in the pool as 18,000 gallons.
18,000 gallons / 6 hours = 3000 gallons per
hour 3000 gph / 60 minutes = 50 gpm
Therefore, you need a pump capable of
delivering a flow rate of 50 gpm under the TDH of the system. The
manufacturer's pump curves described previously will tell us which
pump can do this.
Methods of calculating TDH Here are the
three methods for calculating TDH.
Method 1: Exact values:
If you have the exact specifications of the
pool as built or as proposed, measure all the pipe from the pool,
through the equipment, and back to the pool. Add the equivalent feet
of pipe for all the fittings. Add the feet of head at the desired
flow rate for the filter, heater, and any other components to arrive
at the TDH for the system.
Method 2: Estimated values:
- Suction-side head. Assume 2 feet of head
for each 10 feet the equipment is away from the pool.
- Discharge-side head. Estimate how many feet
of pipe are in the system back to the pool. Double that estimate
to allow for fittings.
- Using the tables, calculate the feet of
head for the total amount of pipe on the discharge side.
- Equipment head. Consult manufacturer's
tables and charts for the desired flow rate (in the example, 50
- Add these three parts together to get the
Let's try a simple example. Let's say our
equipment is 30 feet from the pool (at 2 feet of head per 10 feet of
distance, that makes 6 feet of head). There is about 60 feet of
1/2-inch plumbing between the equipment and the run back to the pool
(doubled is 120 feet). The table says 13.5 feet of head per 100 feet
of pipe equals 1.2 x 13.5 or 16.2 feet of head. The filter
manufacturer says our sample filter has 7 feet of head; the heater
manufacturer says 15 feet of head. Therefore:
- Suction side estimate 6.0 feet
- Discharge side estimate 16.2 feet
- Main drain and skimmer estimate 5.0 feet
- Filter 7.0 feet
- Heater 15.0 feet for a total dynamic head
of 49.2 feet.
Now you can consult various manufacturer's
pump charts to decide which pump will deliver the desired 50 gpm at
49.2 feet of TDH.
Method 3. Measured values:
An easier and more accurate way to estimate
all of this, if the existing pump is operating, is to measure the
vacuum on the suction side of the pump and the pressure on the
discharge side. Plumb a vacuum gauge on the pipe entering the pump.
It measures inches of mercury. Every 1 inch of mercury equals 1.13
feet of head. Plumb a pressure gauge on the pipe coming out of the
pump. It measures pounds per square inch (psi). Every 1 psi of
pressure equals 2.31 feet of head.
Multiply the gauges out accordingly and the
sum of the two gives you the TDH of the system. This might sound
like work, plumbing in two separate gauges, but it really isn't, and
it gives you the most accurate TDH calculation because it takes into
account the dirty filter, the limed-up heater, all the unseen
plumbing. It also allows you to keep an eye on the TDH in the system
at any time and more easily troubleshoot poor performance in the
The running water not only encounters friction
created by pipes and equipment, but the water itself is creating
friction. This friction will strip copper from pipes and heater
components causing all kinds of havoc,9see the section on chemistry,
damages filter grids, and makes DE or sand inefficient (see the
Because of this, most building codes set
maximum flow rates of 8 feet per second through copper pipe and 10
feet per second through PVC. Since heaters all use copper heat
exchangers, use 8 feet per second even if the plumbing is PVC. Los
Angeles County, for example, allows a maximum flow rate of 8 feet
per second on suction pipes of any type. What is feet per second in
terms of gallons per minute?
50 gpm in 1 1/2-inch pipe = 7.9 feet per
50 gpm in 2-inch pipe = 4.8 feet per second
60 gpm in 1 1/2-inch pipe = 9.5 feet per
60 gpm in 2-inch pipe = 5.7 feet per second
By the way, there are a few exceptions to the
rules. Los Angeles County requires pumps to deliver the desired
gallons per minute at 60 feet of head. When sizing pumps, you must
assume at least 60 feet of head regardless of the actual
calculations. In filters, on the other hand, you must use the actual
head as measured. Altitude also affects these calculations. Over
3300 feet above sea level a motor runs hotter, so you will want to
upgrade to the next horsepower.
It is always better to keep the pump and the
motor in good condition for they affect the efficiency of the
system. Keep the motor in good working condition by keeping it dry
and cool. Also do not allow the bad and worn bearings take toll on
the motor. Attend to any leaks as soon as detected in the pumps as
they will eventually affect the motors.
The basic repairs and maintenance of the pump
and motor unit are discussed in the following sections.
When the strainer basket get clogged with
debris and dirt clean it out for this is one sure maintenance
procedure required for pump maintenance. Even small amounts of hair
or debris can clog the fine mesh of the basket and substantially
reduce flow. For this, you have to shut down the system, remove
cover bolts or clamps, clean out hair and filth from the basket, put
the basket back, find a water source to fill the pot so the pump
will reprime easily, check the O-ring, replace the cover, tighten
the bolts or clamps, and restart the system.
Breakage is the other problem encountered at
the strainer pot. If the basket or the pot is broken or cracked, the
basket will permit large debris and hair to clog the impeller or the
plumbing between the equipment components.
Most problems occur in strainer pots when the
pump is operated dry, due to which the case heats up, with no water
to cool it. The strainer basket will melt; the pot cover, if
plastic, will warp; and the O-ring will melt or deform. Replacement
of the parts should be done in such cases.
When gaskets leak, the replacement process is
the same as same as removing the strainer basket. Remove the
strainer pot. Clean out the old gasket thoroughly with no residual
remains. Reassemble the new gasket and strainer pot the same way the
old one came off. Tighten the bolts evenly. Sometimes the bolts are
designed to go through the opening in the pot and volute and are
tightened with a nut and lock washer on the other side. Be careful
in assembling these components.
When removing and replacing the strainer pot
cover, be sure the O-ring and the top of the strainer pot are clean,
because debris can cause gaps in the seal. Sometimes these O-rings
become too compressed or dried out and brittle and cannot seal the
cover to the pot. Replace the O-ring in such case.
All pumps have seals to prevent water from
leaking out along the motor shaft. When these wear out due to
overheating, they are easy to replace. The first thing to do is to
turn off the electricity to the motor at the breaker.
- To access this seal for replacement, remove
the four bolts that hold the pump halves together, it is not
necessary to remove the entire pump from the plumbing system.
- Grasp the motor and pull it and the bracket
away from the volute. Wiggle it slightly from side to side as
you pull back to help break this joint.
- Take your pliers or a wrench and hold the
shaft extender to prevent it from turning. Unscrew the impeller
from the shaft extender using an impeller wrench. You can also
wrap a rag over the face of the impeller so you don't cut
yourself and twist it off by hand. As a last resort, hold a
large screwdriver against the impeller and tap it gently with a
hammer. Use care not to damage the impeller. Use even more care
that the screwdriver doesn't slip and damage you.
- Remove the four bolts that hold the bracket
on the motor. If needed use a hammer to gently tap the bracket
away from the motor.
- Remove both halves of the old seal. Note
how each half is installed so you get the new one back in the
same way. One half is in the back of the impeller and is easily
popped out with a flat-blade screwdriver. The other half is in
the seal plate and motor bracket unit. Lay the bracket on your
workbench with the seal on the bottom. You will see the back of
the seal through the hole in the seal plate. Using the
flat-blade screwdriver once again-put the tip on the back of the
seal and tap it with a hammer. It will pop out easily.
- Install the new seal. First, look up your
pump in the manufacturer's literature or supply house catalog to
determine what model seal you need. Failing that, you can take
the old one to the supply house so they can identify it for you.
There are only three commonly used seals in pool and spa work.
Clean out the seal plate and impeller where you have just
removed the old seal. Use an emery cloth or a small wire brush
and water. Dry each area and apply a small amount of silicone
lubricant to help the new seal slide into place. Install each
half of the seal the same way you removed the old one-white
ceramic of one half facing the glazed carbon ridge of the other
- Gaskets. When you break apart a pump, the
old gasket usually won't reseal. Clean all of the old gasket off
of the seal plate and volute. Scrape it clean if needed with
flatblade screwdriver. Now reassemble the pump the same way you
took it apart, placing a new gasket between the pump halves.
- Check for leaks by starting the pump and
let it run several minutes. A fresh paper gasket might leak for
a few minutes until it becomes wet and swells to fill all the
gaps, but it should stop leaking after a short time. If your job
does leak, take it apart and go over each step again, making
sure the seal halves are seated all the way and that there is no
corrosion or debris left in the impeller or seal plate that
might prevent the new seal from seating completely.
In some pumps where the parts are assembled
differently, you follow the same steps. The clamp is removed to
disassemble the pump halves, and you must remove the diffuser to get
to the impeller. To remove the impeller you can grip it with your
hand and twist it off, but the trick with these units is to stop the
shaft from spinning as you twist off the impeller. There are air
vents in the motor on the end closest to the pump itself. Look in
and you will see the motor shaft. Place a flat-blade screwdriver in
one of the air vents and wedge it against the shaft to keep it from
Alternatively, you can remove the end cap and
look inside as you twist the impeller. You will see the back end of
the shaft, with the start switch attached. Since this switch is
fragile, you must remove it (one screw) to access the slotted screw
in the back end of the shaft. Place the screwdriver in this screw to
keep the shaft from turning as you remove the impeller.
Instead of a gasket, some pumps use an O-ring.
Clean this and lubricate it with silicone before reassembly. If it
has stretched and it seems like there is too much O-ring for the
channel in the volute, try soaking the gasket in ice water for a few
minutes to make it shrink a bit.
Some pumps use a plastic impeller with a
housing that holds half the seal in place. if the pump has run dry
and overheated the pot, this housing might be warped and the seal
will not fit tightly. The only solution is to replace the impeller.
This is a common problem with automatic cleaner pumps, which are not
Remember to use only non-hardening silicone
lube on all pool and spa work. Vaseline or other lubricants are made
of petroleum, which eats away some plastics and papers.
And/Or Motor Removal And Reinstallation
Sometimes it is necessary to remove an entire
pump and motor unit to take it apart or complete a repair. If the
pump is damaged beyond your ability to repair it, you might want to
take the entire unit to a motor repair shop. They can rebuild it as
needed, and you can reinstall it.
Generally, to remove the pump and motor as a
unit first thing is to turn off the circuit breaker. Now you will
need to cut the plumbing on the suction and return side of the pump.
Leave a few inches on both the sides of the cut to replumb it by
When installing or reinstalling the plumbing
between the pump and filter keep bends and turns to a minimum. Also,
do not locate the pump close to the base of the filter. When you
open the filter for cleaning, water is sure to flood the motor.
Lastly, try to keep motors at least 6 inches off the ground, to
prevent it from flooding during rains.
The electrical connection must be removed
before the pump and motor can be disengaged. Now remove the access
cover to the switch plate area of the motor, near the hole where the
conduit enters the motor. Remove the three wires inside the motor
and unscrew the conduit connector from the motor housing. Pull the
conduit and wiring away from the motor and the entire pump and motor
should be free.
If there is an additional bonding wire (ground
wire), it can be easily removed by loosening the screw or clamp that
holds it in place.
Tape off the ends of the exposed wires, and
leave a note on the breaker box, as a warning.
Position the pump as close to the body of
water and as near to water level as possible so it doesn't have to
work so hard. Mount the unit on a solid, vibration-free base. Make
sure there is adequate drainage in the area so that when it rains or
if a pipe breaks the motor won't be drowned. Bolt or strap down the
Plumb in both suction and return lines with as
few twists and bends as possible, to minimize head. A gate valve on
both sides is advisable to isolate the pump when cleaning other
components. A check valve is essential if the unit is well above
water level. Plumb the unit far enough away from the filter that it
won't get soaked when you take the filter apart.
A Pump Or Motor
Having learned how to remove and break down a
pump and motor in the previous sections, replacing any of the
components is simply a matter of disassembling the pump down to the
component that needs replacement, getting a replacement part, and
reassembling the unit. Of course, if the entire pump and motor is to
be replaced, you purchase the replacement as a unit and plumb it in
as previously described.
Sometimes the motor will trip the circuit
breaker when you try to start it. If this happens it is usually
because there is something wrong with the motor; however, it could
be a bad breaker or one that is simply undersized for the job and
has finally worn out. To replace the motor here are the procedure:
- Break down the unit as described in the
section on changing a seal. Remove the shaft extender by
removing the allen-head setscrews and pulling the extender off
the motor shaft. Sometimes this might need persuasion. Use your
large flat-blade screwdriver to pry the extender away from the
motor body. Sometimes corrosion will eat away at the setscrews
and extender-if it is too tough to remove, replace it.
- Before sliding the shaft extender on the
new motor, clean the motor shaft with a fine emery cloth such as
you might have in your copper pipe solder kit. Apply a light
coat of silicone lube to the shaft. When you put the extender on
the motor shaft, the setscrews go into a groove that runs along
the shaft. This groove allows the screws to grip and not slide
around the shaft.
- Now slide the new extender in place, lining
up the setscrews along the channel, but do not tighten the
setscrews. When you have reassembled the bracket and seal plate,
seal, and impeller, you can adjust the impeller to just barely
clear the seal plate face, then tighten the setscrews. Be sure
the impeller is screwed tightly onto the shaft extender before
making this adjustment. If it is loose, when the motor starts it
will tighten the impeller, by turning it tighter against the
extender, thereby tightening it against the seal plate, seizing
up the unit.
- Secure the shaft extender with your pliers
or 3/8-inch box wrench and lay a rag over the impeller. Firmly
hand tighten it. Reassemble the remaining pump parts and/or
replumb the entire unit back into place.
- You can access the electrical connections
through the switchplate cover in the front end bell.
The first and most common motor problem is
water, which may be due to on of he many reasons, like rain, filter
cleaning or breaking of the pipe. In all cases, dry the motor and
give it 24 hours to air dry before starting it up. Even small amount
of moisture can short the motor. The basic problems beyond this are
Motor will not start
Check the breaker panel, and look for any
loose connection of the wires to the motor. Sometimes one of the
electrical supply wires connected to the motor switch plate becomes
dirty. Dirt creates resistance that creates heat which ultimately
melts the wire, breaking the connection. Similarly, if the supply
wire is undersized for the load, it will overheat and melt. Clean
dirty switch plate terminals and reconnect the wiring.
Motor hums but will not start
The impeller may be jammed with debris. Turn
off the breaker, and spin the shaft by hand. If it won't turn
freely, open the pump and clear the obstruction. If it does spin,
check the capacitor.
Check the capacitor for white residue or
liquid discharge. Either is a symptom of a bad capacitor. To replace
the capacitor, remove the cover that holds it on top of the motor.
This cover is held in place with two screws. The two wires are
attached to the capacitor with simple push-on and pull-off bayonet
clips. Install a new capacitor.
The motor may hum and yet fail to run because
of insufficient voltage. Use a multimeter to check the actual
voltage and consult the utility company if there is a problem.
Loud noises or vibrations
This is most often caused by worn out
bearings. Take the pump apart and remove the load (impeller and
water), If the motor still runs loud or vibrates, it is the
bearings. Take it to a motor shop, or better still, replace the
motor, unless the motor is relatively new or is still under
warranty. This problem can also be caused by a bent shaft, although
that is not common.
The breaker trips
Disconnect the motor and reset the breaker.
Turn the motor switch or time clock on switch, back on and if it
trips again, the problem is either a bad breaker or, more likely,
bad wiring between the breaker and motor. Be very careful with this
test. Switching the power back on with no appliance connected means
you are now dealing with bare, live wires. Be sure no one is
touching them and that they are not touching the water, each other,
or anything else.
If the breaker does not trip when conducting
this little experiment, the motor is bad. This usually means there
is a dead short in the windings and the motor needs to be replaced.
Water can cause this.
Priming is starting the suction that gets
water moving through the pump thus creating circulation in the pool.
Most of the modern pumps are self priming, but when the water get
drained from the pump it sometimes needs to be reprimed before it
can get started.
Let's go through the steps to prime the pump
in most of the pool and spas:
- Check the water level in the pool. Water is
sometimes lost during maintenance and there might not be enough
in the pool to fill the skimmer. Or some times the pump will not
prime unless filled to the very top of the skimmer.
- Check the water path. Many a times, priming
problems are not related to the pump, but to some obstruction.
Check the main drain and the skimmer throat for leaves, debris,
or other obstructions. With the pump turned off, open the
strainer pot lid and remove the basket and dispose off the
leaves and debris. Last, make sure that once the pump is primed
be sure all valves are open and that there are no other
restrictions in the plumbing or equipment of the pump.
- Fill the pump. Always fill the strainer pot
with water and replace the lid tightly so air cannot leak in.
Keep adding water until the pot overflows so you fill the pipe
as well as the pot. Sometimes the pump is installed above the
pool water level so you will never fill the pipe unless a check
valve is in the line as well. Quickly, just fill what you can
and close the lid.
- Start the motor and open the air relief
valve on top of the filter. The pump is primed if all the air is
replaced with water and the normal circulation begins. It is
advisable to wait for couple of minutes for the pump to prime
itself, but at the same time make sure that you do not overheat
by running a dry pump.
Sometimes repeating this procedure two or
three times will get the prime going. If there is a check valve in a
long run of pipe, each successive filling of the pot pulls more and
more water from the pool, which is held there each time by the check
valve. Also, if it is warm outside, the air in the pipe might expand
and create an airlock. The repeated procedures might finally
dislodge the air.
The blow bag method
When basic priming fails, try a drain flush
bag, also called a blow bag. The drain flush is a canvas or rubber
tube that screws onto the end of your garden hose. Slip this into
the skimmer hole that feeds the pump and turn on the hose.
The water pressure makes the bag expand and
seal the skimmer hole so the water from the hose cannot escape and
must feed the pump. After running the hose a minute or two, turn on
the pump. When air and water are visible returning to the pool, pull
the drain flush bag out quickly, while the pump is running, so pool
water will promptly replace the hose water.
This method is not effective if the skimmer
has only one hole in the bottom, for this hole is connected not only
to the pump but also the main drain. The forced water from your
drain flush bag will take the line of least resistance and flood
through the main drain rather than up to the pump. In the two hole
skimmer, the hole furthest from the pool usually is plumbed directly
to the pump. Your drain flush bag in this hole will give good
Filter filling method
Another method is filter filling. Open the
strainer pot, turn on the motor, and feed the pot with a garden
hose. Open the filter air relief valve and keep this going until the
filter can is full (water will spit out of the air relief valve).
Close the air relief valve, turn off the motor and garden hose, and
quickly close the strainer pot. Open the air relief valve. The
filter water will flood back into the pump and the pipe that feeds
the pump from the pool. When you think these are full of water, turn
the motor back on. The pump should now prime.
Detecting air leaks
When none of the above mentioned methods work,
then there is the problem of air leaks. The problem might be that
the pump is sucking air from somewhere. Air leaks are usually in
strainer pot lid O-rings, or the pot or lid itself has small cracks.
The gasket between the pot and the volute might be dried out and
leaking. Of course, plumbing leading into the pump might be cracked
and leaking air.
If any of these components leak air in, they
will also leak water out. When the area around the pump is dry,
carefully fill the strainer pot with water and look for leaks out of
the pot, volute, fittings, and pipes. Another way is to fill and
close the pot, then listen for the sizzling sound of air being
sucked in through a crack as the water drains back to the pool.
Sometimes there's just no easy answer. This
time remove the pump and carefully inspect all the components,
replace the gaskets and O-rings, and try again.
Many pumps employ threaded T-shaped bolts that
secure the lid to the strainer pot. Sometimes these corrode and snap
off, with part of the bolt remaining in the pot. If part of the
broken bolt extends above or below the female part on the pot, try
using pliers, especially Vise-Grips, to grasp the broken section and
twist it out, like removing a screw. Replace with a new T-bolt.
If this doesn't work, take your tap and die
set or electric drill and tap a small hole inside the broken piece,
then use your Phillips-head screwdriver to grip inside the hole and
twist out the broken piece. If all else fails, remove the pot from
the pump and take it to a machine shop to be tapped out and
Reverse flow problem occurs with many pumps.
But it has been observed that reverse flow problems does not occur
with semi-open face impellers. When the pump is pushing the water,
the air may get trapped in the filter due to either the leak in the
system or due to improper blending of the filter with the new
installation. While the running pump is pushing water against the
trapped air bubble in the filter, the power to the pump motor is
interrupted. The moment the power goes off the pump stops, releasing
the bubble of air. This instant release of air forces the column of
water between the pump and filter to reverse and flow backwards
toward the pump, entering the discharge side of the filter. This
reverse flow of water into the discharge side of the pump starts the
impeller turning in the wrong direction. Within a few short seconds
the pump impeller can be turning at high speeds driving the motor in
reverse as well.
When power is restored and the motor does
start while turning in the wrong direction, the torque of the motor
can be great enough to loosen and spin the impeller from the shaft,
stripping the threads.
Reverse flow is a very rare occurrence and as
far as we can determine it can be overcome simply by using a check
valve between the filter and pump. This is the most effective way to
prevent it. Several large pump manufacturers have recognized the
same occurrence and to prevent reverse flow have been securing the
impeller to the motor shaft. This, of course, prevents the impeller
from stripping its threads.
A look at the manufacturer's literature or
catalogs at your local supply house will reveal that all pumps are
variations on two basic concepts.
Motors to drive these pumps are made by
several manufacturers as well, although I know of none who make both
pumps and motors. Century, Franklin, A.O. Smith, General Electric,
and others make all the various styles and horsepower of motors
needed to run modern and older pump equipment. Some of the styles
you will encounter and need to specify when replacing are as
follows. Remember, the nameplate on the motor gives you this
information, but it is often obscured or missing, so be familiar
with these types.
If you look at the face of the motor, the end
with the shaft, you will note a definite pattern in the casting that
looks like the letter C. The shaft is threaded, meaning it has male
threads on the end of the shaft to receive the female threads of the
impeller; or keyed, meaning the shaft has no threads, but rather a
channel that runs the length of the shaft to accept the setscrews.
Look at the end of the motor that has the
shaft. This style of motor includes a flared bracket, square of
course, that accepts the seal plate of the Sta-Rite pump and the
corresponding motor. These are only made with threaded shafts
because they work only with the type of pump that uses a threaded
These are not in use much anymore. The uniseal
motor includes a flange like the square flange for application with
a uniseal-type pump.
This is the motor used on indoor spa booster
pumps and fits that particular style. Jacuzzi makes a number of
pumps that use the 48 frame. These are all threaded shafts.
Now let us examine some of the different
characteristics of the motors.
The housing at each end of the motor is called
the end bell. It is made of aluminum or cast iron, the latter being
more expensive. Iron rusts and aluminum doesn't and aluminum more
efficiently disperses heat away from the motor, thereby prolonging
its life. Some manufacturers give you a choice within each type of
The full-rated motor operates to its listed
capacity (1 hp, 2 hp, etc.). The up-rated motor has a similar
horsepower rating but functions to even higher standards if called
upon (see the section on service factor). This might be useful if
the pool or spa gets full of leaves, for example, and the motor is
required to work against increasing loads until someone clears out
the debris. By checking the service factors, you might be able to
get a 1/2-hp up-rated motor that is able to perform as well as a
1-hp full-rated motor.
As the name implies, this motor includes a
switch box to wire it for two-speed operation. Spas, for example,
often use a two-speed motor with the lower speed for circulating and
heating, and the high speed for jet action. Wiring instructions are
printed on the motor as described previously.
As described previously in the section on
motors, the so-called energy efficient motor is, in fact, a design
that saves electricity over a comparable motor of standard design.
The special characteristics of pumps and motors for automatic
cleaner boosters are discussed in the section on automatic cleaners.
Protective covers are made to fit over motors
and are designed to keep direct sunlight and rain off the motor
housing. They are made from either plastic, metal, or foam rubber.
In fact, the motor is designed to do this itself. You will notice
that the motors in the illustrations all have air vents on the
underside. The greatest danger to a motor is flooding of the
equipment area in heavy rain or when opening a filter, or allowing
water from the ground to get up into the motor. This will short out
the windings and void any warranty.
There are essentially two types of submersible
pump and motor combinations that you will encounter.
Sometimes you need to drain a pool or spa.
Several manufacturers make pump and motor units with long,
waterproof electrical cords, that can be completely submerged. The
suction side is at the bottom of the pump, as if a regular pump and
motor unit were stood on end with the motor on top and the pump on
the bottom. The return line is sized to be attached to your vacuum
hose. Smaller units are connected to a garden hose to feed water out
of the pump.
Pumps And Motors
Fountains and small ponds use small
submersible pump and motor units that contain all of the same
components as the larger ones, except that their size is small.
These have waterproof electrical cords so they can be submerged in
the body of water.
Both high- and low-volume types contain the
same components as the pumps and motors described earlier and are
repaired in much the same ways. Submersibles have more crucial and
tricky seals and gaskets, however, because leaks in these mean
electricity in the body of water that can be fatal to both the motor
and you. Any repair of the pumps should be done by certified
As with any electrical appliance, you can
easily calculate the cost of operation. Electricity is sold by the
kilowatt-hour. This is, 1000 watts of energy each hour. You know
that volts x amps = watts, so you can look at the motor nameplate
and see that the motor runs, for example, at 15 amps when supplied
with 110-volt service, and 7 amps when supplied by 220-volt service.
Let's say the pump in our example is running
on 220-volt service-220 volts x 7 amps = 1540 watts. Looking at an
electric bill, you learn that you pay 15 cents per kilowatt-hour. As
noted, a kilowatt is 1000 watts, so if you divide 1540 watts by
1000, you get 1.54. That is multiplied by your kilowatt rate (15
cents), equaling 23 cents for every hour you run the appliance. If
you run the motor eight hours per day, that means 23 cents x 8 hours
= $1.84/day. Over a month, that equals 30 x $1.84 $55.20/month.
Pumps And Motors For Spas
Pump and motor units that provide only jet
action for spas generally are not equipped with a strainer pot and
basket, otherwise they are the same as other units, that are used
for the pools. Some units are designed to perform two functions and
therefore run at two speeds. They run at high speed (3450 rpm) to
provide jet action. But at a low speed (1750 rpm), they also
circulate, filter, and heat the water and would have a strainer pot
To operate efficiently, spa jets require 15
gpm running through each one. Therefore, if you have a system that
delivers 60 gpm, you can install up to four jets. Also, each jet
requires 1/4-hp from its pump and motor, thus four-jet spa would
need at least a 1-hp unit.
Remember, this assumes the pump is doing no
other work. If it is pushing water through the filter and heater
before getting back to the jets, or if the equipment is more than 20
feet from the spa, then some power will be lost and you will need to
calculate more than 1/4-hp per jet.
When planning a system or replacing equipment,
many codes require that a spa to turn over completely two times per
hour, so be sure the pump can handle that, especially when the
filter gets dirty and head increases.