or Public Pools
A commercial or public pool or spa may be
defined as one that is used by the public, may they be members of
club or any residential establishment or communities and schools.
Particular equipment, design, and maintenance standards are
mandatory for commercial pools. Many building codes and health
departments have mandatory rules and standards for commercial pools.
There are rules about minimum chemistry standards, covers, safety
equipment, and turnover rates enforced by state and local
jurisdictions. Public swimming pools are usually operated by
government agencies and are under constant scrutiny by health
Health inspectors visit the pool at least once
a year in most areas. Because of liability issues, health inspectors
may close a commercial pool until violations are corrected or impose
fines if compliance is not met.
Swimming pools are classified in most states
from public to private pools. Private swimming pools are maintained
by homeowners or residential establishment for the use of family and
Semipublic swimming pools are operated by a
private person, a business or an organization. It has restricted
number of users. These pools are generally found in summer camps,
hotels and motels, housing complexes, private club or athletic club.
Commercial or public pools are operated by
government agencies such as communities and school. It might be ten
times larger in the size and volume then private pools. Competitive
swimming pools, for example, are usually 50 meters in length by 23
meters in width. The free-form pool with multiple rockscapes and
waterfalls are becoming more popular in forms of commercial or
The volume calculations for commercial pool
become simple if the pool is divided into sections and then making
It is important to calculate volumes of water
in large pools. The accuracy of the estimate becomes critical with a
commercial pool, because liability and public health are involved
and also because when dealing with large numbers, even a small
percentage error may result in mistakes of thousands of gallons and
therefore significant errors in chemical applications, turnover
rates, and other maintenance calculations.
With commercial volume calculation, it is
important to estimate the slopes of the sides and floor to get
correct volume estimates. It is best to consult the pool plans or
builder to determine the exact calculation. It is best achieved by
calculating the volume of each section (dividing commercial pool in
different sections and calculating the volume for each section) By
adding the volume of each section gives us the total pool volume.
In dealing with commercial volume calculations
be careful that errors in estimating the slopes of the sides and
floor can result in volume estimates that may lead to thousands of
gallons volume estimate errors.
There are numerous formulas and guidelines
establishing maximum user or bather load. Some codes consider
recirculation flow rates in gallons/minute per swimmer and some
differentiate between indoor, outdoor, shallow and deep end pools.
Other consideration is given to the size of surrounding decks or to
special equipment, such as slides and diving boards. Pool operator
should consult health codes for the appropriate formulas and to the
standards for which the pool was designed.
In general, if the local codes are not
- One bather per 15 square feet of surface
area in portions of the pool that are 5 feet deep or less.
- One bather per 20 square feet of surface
area in portions of the pool that are more than 5 feet deep.
- Subtract 300 square feet from the total
surface calculations for every diving board.
- For example, the shallow end of the pool is
40 feet x 20 feet = 800 square feet; 800 / 15 = 53 bathers. The
deep end is 40 feet x 80 feet = 3200 square feet. There is one
diving board, so you deduct 300 square feet, arriving at 2900
square feet; 2900 / 20 = 145 bathers. The total occupancy of
this pool is 53 + 145 = 198.
The public pools are used by many bathers at
any given time. The question that arises is how much water is
displaced by the volume of people. This question determines the flow
rates of replacement water, surge chamber requirements.
If the pool is fitted with an overflow drain
to waste, the bather load will displace the water out of the pool or
spa. When the bathers leave, the water level might drop below the
skimmer and the pump could run dry. Obviously this would be even
more likely to occur in a commercial spa.
Usually a typical bather will displace 2 cubic
feet of water fully submerged. But bather at the shallow end are
usually only partially submerged, while bathers in the deep end are
almost completely submerged.
The bather at shallow end displaces 75% of 2
cubic feet each (0.75 x 2 = 1.5 cubic feet each).
The bather at deep end displaces 90% of 2
cubic feet (0.9 x 2 = 1.8 cubic feet each).
So the displacement for all bathers should
allow enough water to be diverted to surge chambers.
Though most equipment for the commercial pool
resemble the smaller versions used by residential installations like
the pumps, air blowers, heaters, cleaning, and other equipment, they
are often built of heavy-duty materials and increased capacities.
The following equipment and supplies are unique to commercial water
Water in large commercial pools is displaced
into a holding tank called a surge chamber, when heavy bather loads
displaces a great deal of water. When bathers leave the pool and the
water level drops, water from the surge tank is pumped back into the
pool. When there is water loss due to splashing and wetting of the
body, replacement water is directed into the surge chamber, where
the level of the pool is monitored. Each surge chamber is designed
differently, but the basic concept remains the same.
Large pools require a slurry tank or feeder
where DE is mixed with water and is pumped at an even rate into the
filter to precoat the grids.
Slurry feeder is simply an open concrete pit
in the pool equipment room where this mixing takes place. A
motorized paddle mixer called an agitator, is used to keep the DE
suspended in the water, which is then pumped into the suction flow
of the pump and sent to the filter grids. There is other system that
uses a slurry tank, from which the mixture is vacuum fed to the
pump, or a pressure system where the mixture is forced into the
system. Modern systems use injectors and various pumps for
measuring, mixing, and moving the mixture, but the objective and
components are the same on each type. As with any DE precoating, the
filter must first be cleaned, then the appropriate amount of DE is
applied, followed by normal filtration.
DE, cartridge, and sand filters are all made
for large commercial pools and spas. When one large filter is
inadequate, several filters are plumbed together in series with a
Cartridge filters are also manufactured for
commercial use, but as discussed in the chapter on filters, they
have not been widely adopted because of the large amount of
cartridge surface area required to filter large bodies of water.
Cartridges can also be difficult to clean, the pleating creating
crevices in which oils and dirt can become lodged.
Commercial filtration generally requires
pressure gauges on the incoming and outgoing plumbing of the pump
and filter. Sight glasses are often required on waste lines and the
outflow plumbing of the filter. Flow meters might be required on the
heater and filter plumbing as well. Make sure these are always
clean, free of leaks, readable, and reflecting accurate pressures
Even distribution of sanitizer is a problem in
the large volumes of water found in commercial pools. Because
bathers are likely to use the pool or spa immediately after
servicing, it is important to make sure chemicals are not lingering
in harmful concentrations at any point in the water.
Chlorine gas is the most efficient and least
expensive sanitizer. Injecting it into the circulating water is an
effective way of gradually adding chemical to a pool or spa. For
commercial pools it is the preferred method of sanitization.
In a typical chlorine gas feeding system, the
gas is supplied in cylinders that discharge the chlorine gas through
a pressure regulator, volume control (to control the ultimate
strength of the chlorine mix), and visible volume meter to a water
reservoir. When the gas is injected, it mixes with the water to form
a solution that is then pumped into the circulation system for
delivery to the pool or spa. By regulating the time of operation and
volume of gas delivered, the sanitizing of the water can be managed.
The incoming water supply might be fill water for the pool or part
of the circulation water diverted for this purpose.
Some installations make their own chlorine,
considering how expensive it is to sanitize a large pool or spa and
how relatively inexpensive salt, electricity, and water are.
Chlorine generators produce chlorine gas by electrolysis. The
generator consists of a plastic tank with two compartments separated
by a filter-type membrane. The larger side, which includes a
positively charged electrode (called the anode), is filled with a
salt (sodium chloride) and water solution. The smaller compartment,
which includes a negatively charged electrode (called a cathode), is
filled with distilled water or municipal water (If it is not too
hard). The membrane allows electricity to pass through but restricts
the chemicals produced to one side.
Chlorine gas is generated in the salt solution
compartment when the electricity separates the chlorine from the
sodium. The gas rises above the water and some passes through the
membrane, mixing in the smaller chamber with the fresh water to form
sodium hydroxide (which is drained off periodically). Hydrogen gas
formed in the process is vented out of the generator. Salt is added
periodically to recharge the system. The chlorine gas is then
injected through plastic plumbing into the circulation plumbing. The
electrical current is supplied through a transformer that converts
110- or 220-volt ac into 12-volt dc. Regulating the current
regulates the volume of chlorine produced. Some variations of the
chlorine generator include systems that produce the chlorine right
in the circulation water flow for direct application to the pool or
All pool or spa equipment rooms should be kept
clean and neat, but this is critical in the commercial equipment
room. Chemicals should never be stored near equipment, where heat or
water leaks could mix with the chemicals, with toxic results.
A sump pump should be installed in a pit in
the floor of the equipment room. Since leaks in commercial plumbing
can be very substantial, a submersible pump with an automatic float
switch should be provided that will drain water from the room to a
waste line. Commercial equipment is expensive and water rising from
a major leak can cost much more than a sump pump.
Most building codes require that the deck be
clear and unobstructed all around the pool or spa, with any
furniture set back at least 5 feet. This provides a margin of safety
so people don't trip and fall in the pool and so that bathers can
easily exit the pool or spa at any point.
Special safety equipment is usually required
by health departments. These might include a shepherd's crook, toss
ring, and first-aid kit. The toss ring must be attached to a rope
that can reach to the greatest distance of the pool. The shepherd's
crook, attached to a sturdy pole of at least 16 feet, must have at
least an 18-inch opening and be able to support up to 150 pounds.
Many jurisdictions also require a floating safety rope across the
pool at the point where the major break in the slope of the floor
begins, usually about the 4- to 6-foot depth.
Before performing any remodeling procedure on
a commercial pool, check the building codes for safety requirements.
If you are adding equipment, like installing a diving board, be sure
you know the requirements of water depth and area clearances. Many
jurisdictions require a minimum of 10 feet of water depth, 15 feet
of clearance above any part of the diving board surface, 10 feet
clear on each side of the board, and at least 16 feet of horizontal
water surface in front of the furthest reach of the board.
For any commercial installation, you must
obtain a copy of the codes and regulations applicable in your area.
The following are a few common standards to look for.
For health and safety reasons, most
jurisdictions require that the circulation equipment be operating
whenever the pool is open to bathers.
Service logs must be maintained and kept
available in the equipment room for inspection so that a health
department inspector can verify compliance with regulations and
compare servicing to water testing results.
Always close the pool or spa to users whenever
you are performing cleaning or chemical service. Don't give in to
the demands to use the pool when you feel the pool is unsafe for any
reason. Many regulations require deck and pool lighting of certain
specifications, whether the pool is used at night or not. Make sure
that the bulbs are working and the timers are operating correctly.
Make sure access to the heater temperature
controls is locked. If you leave controls exposed, someone will turn
perhaps creating dangerous conditions for users. Lock away time
clocks and chemical supplies.
Drains, gutter suction ports, deck skimmers,
and other lines must be covered or fitted with a grate.
Some jurisdictions require minimum visibility
so that any injured person at the bottom will be seen. Some
standards call for visibility at a certain level, others call for
the main drain cover to be clearly visible.
Some jurisdictions require (and it is a good
idea in any case) that you be certified by a recognized professional
organization to maintain commercial pools. Check with the
authorities in your area to learn what training they recognize and
Flow meters record the flow rate in a
particular pipe or piece of equipment. Inside, a small lead weight
rises and falls depending on the flow of water in the line. One end
of the flow meter is male threaded for easy installation into a
female threaded opening in a pipe.
Flow meters are generally used in commercial
installations where health department or building inspectors test
the system by the rate and volume of water flow. Some codes require
a flow meter be installed in the system.
To install the flow meter, cut the pipe and
plumb in a T fitting to reconnect the pipe. Two ends of the T are
used in reconnecting the pipe, and the third opening of the T is
plumbed with a female threaded reducer to make the opening the same
size as the male threaded end of the meter, which is then screwed
into place. Apply PTFE tape to the male end to prevent leaks.
Another method is to drill a hole in the pipe
that is slightly smaller than the diameter of the male threaded end
of the flow meter. Because the PVC is softer than the metal end of
the meter, when you apply pressure and screw it into the pipe it
will self-tap. These installations usually leak.
You can use this method with copper plumbing
because although the copper is soft, it is less likely to strip when
you screw in the flow meter. Some meters fit loosely in the hole
sealed with a gasket and are held in place with pipe clamps.
Flow meters are not always accurate and should
be used as a reference in conjunction with other observations you
make about a system.