Pool and Spa
How To Change Or Replace
Underwater Lights and Bulbs For Swimming Pools And Hot Tub Spas
Lighting is essential if the pool is to be
used at night. External lighting of your pool, spa, or water feature
is possible with a variety of high- and low-voltage systems. For
installation and maintenance of external systems, it is recommended
you consult your local electrician. For lighting the water from
within, however, there are also a variety of options. This is where
the water technician needs to be an expert.
Figure 15 shows a typical pool or spa light
housed in a stainless steel conical shaped fixture, about 8 inches
in diameter by 6 to 10 inches deep. The fixture is mounted in the
wall of the pool or spa in a container called a niche.
Like the lights in your house, pool and spa
light fixtures have a standard, screw-in socket for a bulb (in fact,
your household 100-watt bulb will work in a 120-volt pool or spa
fixture). The cord that supplies electricity to the fixture is
waterproof and enters the unit through a waterproof seal. There are
no user serviceable parts in the cord, seal, or fixture except for
changing the bulb. Although the correct term is lamp, will use the
more common expression bulb. Fixtures and bulbs are available in 120
or 240 volts, but 120 volts is most common for residential use.
Bulbs generally run from 300 to 500 watts.
Fixtures are sold with cords of 10 to 100
feet, so you need to know the distance from the light niche to the
junction box to determine what you need when purchasing a
replacement fixture. A simple rule of thumb is to buy the next
longer length than you think you need, because you can always use
the cord for something else and the few extra bucks is cheaper than
getting one a little too short and making another trip to the supply
Smaller versions of these fixtures are
available for spas. They come in 120 or 240 volts, but usually
employ smaller-based specialty bulbs that might screw in or have
bayonet-type sockets. A quartz or halogen bulb will give you the
most light from a small low-wattage bulb. These new technology bulbs
are very expensive but save energy and need replacement less often
than hotter, higher wattage standard bulbs.
You might encounter very old fixtures that are
basically designed the same as modern ones, but they have a mogul
base. The socket for these are also female threaded, but they are
about twice the diameter to accommodate bulbs with that mogul-style
base. Replacement bulbs are still available for these fixtures.
Light fixtures are sealed to be completely
watertight, so the air inside reaches extreme temperatures unless it
is cooled by contact with the water. Never turn these lights on if
there is no water in the pool.
Most fixtures have lens overlays available in
a variety of colors. These are plastic lenses that snap over the
glass lenses to make the light blue, green, or whatever color. Being
very thin plastic, these too will quickly melt if the light is
operated out of the water.
Fixtures are held in the wall of the pool or
spa in a light niche. A niche is a metal can large enough to contain
the fixture, cemented watertight to the side of the pool. A
waterproof conduit leads away from the niche to above the water
level out of the ground to a junction box.
Installation of new lighting needs following;
- Access to the electrical connection
- Light fixture
- Light bulb
Pool lights require fixtures that have a
standard, screw in socket, just like a normal household bulb. A
water proof cord supplies electricity to the fixture, and enters
through a water proof seal. The only serviceable part inside the
fixture is the light bulb. Fixtures and bulbs come in 120 or 240
volts. 120 volts are the most common for residential use. If the
fixture becomes rusted or otherwise damaged, it cannot be fixed. The
entire fixture has to be replaced.
Electrical work must be perfect and in
accordance to local, state and national codes. Codes may vary from
state to state. Be sure to hire a competent licensed electrician to
complete the work needed.
Since you probably won't be installing too
many light niches on new pools, will outline in next section the
procedure for replacing a fixture when it rusts out or otherwise
Fixtures come with attached, water proof cords
of 10 to 100 feet. Know the distance from the light niche to the
junction box before you purchase a replacement fixture. Buy a longer
cord than you think necessary and cut it to fit. As with all
electrical repairs, turn off the power to the fixture at the circuit
breaker and tape over it so no one turns it back on while you are
The steps involved are:
- Disconnecting the Wiring
- Removing the Old Fixture
- Cutting of the Old Fixture
- Preparing the New Fixture
- Pulling the New Cord
- Installing the New Fixture
Subsequent sections describes above steps to
replace a fixture.
Turn off the power source at the breaker. Find
the junction box. On older pools, this will be in the deck directly
above the light niche, often under a 4-inch diameter stainless steel
(or bronze) cover plate that is held in place by three screws that
probably have rusted or stripped heads, making them impossible to
Later building codes required the junction box
to be at least 5 feet from the edge of the water and 18 inches above
the surface of the water, so on more recently constructed pools,
look in the garden directly behind the light niche and you will
often find it sticking up there.
A typical junction box (simply called a
J-box). Remove the four screws and take off the cover. Three wires
come into the box from the breaker or switch and three go out of the
box to the light fixture. The three to the light fixture will be
individually insulated, colored white, black, and green, and are
bound together with a single rubber sheath that waterproofs the
package. This is the cord of the light fixture as described
previously. Disconnect the three wires. Unscrew the cord clamp.
the Old Fixture
Lean into the pool and remove the face rim
lock-screw (retaining screw) from the faceplate that holds the
fixture to the niche. The top of the fixture will float outward, the
bottom is hooked into the niche and can be lifted out.
Uncoil the excess cord to give you enough
slack to raise the fixture out of the water onto the deck. Go back
to your j-box and tug at the cord of the fixture. If you see the
cord move at the fixture end, you know the replacement is an easy
one. If it's tight, follow the steps outlined later (see tight
off the Old Fixture
Cut the cord where it enters the old fixture.
Strip off the rubber sheath, back about 6 inches. Remove the string
or paper threads that run alongside the wires (these were put in the
cord to add strength for when you pull on it). Remove the insulation
from each single wire back about 6 inches.
the New Fixture
Remove the new fixture from the box and float
it in the pool. Take the wires of the new fixture and strip the cord
back as described in next section. Now bind the wires of the new
cord to the ones of the old, folding each wire over as if to make a
hook, then connecting the two (like two fishing hooks) and twisting
the loose end around the base wire. Use electrical tape to cover the
exposed wire, wrapping it tightly and thoroughly.
Don't tape so much that you make a connection
thicker than the cord itself. It won't pass through the conduit
easily. The idea is to make a union of the wires that will not
separate when you pull.
Lay the cord out freely into the water. Pull
the old cord at the J-box until you have pulled the connection and
the new cord through. Some niches have the conduit connector in the
top of the niche pointing upward at an angle, so when pulling the
cord, it might snag at your connection.
To solve this problem, have someone lean into
the pool and angle the cable down into the water, at the same angle
as the conduit connector itself. That person can feed the line as
you pull from the other end. Keep pulling until you have enough cord
left with the fixture for it to easily reach up to the deck for
future bulb-changing access. Now untape your connection and remove
the old wire.
the New Cord
If the cord won't budge from either direction,
the cord might have swelled from age, heat (electricity creates
heat), or moisture. Try pouring tile soap down the conduit from the
J-box. You might have to let it sit overnight to slither all the way
along the conduit and be effective. Some service technicians use
oil, but whatever you use will eventually end up in the pool.
Another trick is to use leverage. Place a long
2-by-4-inch board down into the pool and run the cord up along its
length. Using the edge of the pool coping as a fulcrum, try to pry
the cord away from the fixture or get your local electrician to help
you with his wire pulling levers. Another trick is to cut the cord
as low as possible at the J-box side of the conduit. Using your
drain flush (blow bag) and the garden hose, try forcing water from
the J-box to the pool through the conduit to loosen the cord.
Compressed air might also work. Be careful not to exert too much
pressure with these techniques, however, because you might crack the
conduit, which might be brittle PVC or thin, rusting copper.
Sometimes the cable comes out, but the new one
tears off as you are pulling it. Remove the new cord and use an
electrician's snake to run through the conduit, starting at the
J-box and working toward the pool. When it comes out the other end,
hook the wires of the new fixture to it and try to pull them through
the New Fixture
Reach into the pool again and coil the excess
line around the fixture, then reset the fixture in the niche.
Replace the lock-screw on top.
Sometimes, particularly if the fixture is way
below the waterline, you might have to get into the pool to loosen
or reset the fixture. If you're on the deck and having trouble
lining up the face rim lock-screw with the hole of the niche, use a
piece of coat hanger wire. Slide it through the hole on the
faceplate and into the hole of the niche. Slide the fixture into
place and the holes will line up for the screw. Remove the wire and
insert the screw. Cut off any excess cord at the J-box, leaving
enough to make a good connection with the supply wires. Reconnect
the wiring and close the J-box. Test the fixture.
The most important factor in bulb replacement
is to maintain the waterproof integrity of the fixture. Follow each
step carefully to avoid leaks that will not only damage the new bulb
and fixture, but might also lead to electrical shock of the next
- Turn off the power, then get the fixture up
on the deck as described previously.
- Remove the lens that is held in place by a
clamp or a set of screws. Gently pry the lens away from the
fixture, taking care not to gouge the lens gasket.
- Replace the bulb. Inside some fixtures you
will find a bare coiled spring wire. This is non-electrical but
is designed to break a circuit. Notice that without a bulb in
place, the spring lays to one side of the fixture. Hold it up
against the opposite side and screw in the new bulb. The spring
lays on the bulb itself. If the bulb bursts when in use, the
spring sweeps across the filament, cutting the electricity in
the circuit. In this way, if water has gotten into the fixture,
a live electrical circuit won't stay in contact with the water,
ultimately electrocuting someone in the pool.
- Now place the fixture on the deck and turn
on the light to make sure your new bulb works. Never operate a
closed fixture out of the water, but with the lens off, the heat
can escape without problem.
- Reassemble the fixture. Check you may need
a new gasket. After long use, heat, and harsh chemicals, the old
one is probably compressed, and if it doesn't fail immediately,
it might fail before the next bulb change.
- In reassembling the faceplate, if it has
the series of screws, tighten them on opposite sides until you
have done them all. This applies even pressure and prevents gaps
in the gasket that will ultimately leak.
- Lay the fixture back in the water. Hold it
underwater for several minutes to make sure it doesn't leak. A
few bubbles might rise from air trapped under the lip of the
faceplate, but a steady stream means the fixture is filling with
water. Take it apart again and dry it thoroughly. Go back to
step 4 and be more careful.
- If it passes the leak test, turn it on for
a few seconds before putting the fixture back in the niche.
During reassembly or testing you might have banged the unit
around enough to break the bulb or its delicate filament, or you
might have a bad bulb. Remember, the closed fixture depends on
water for cooling, so conduct this test for literally no more
than two seconds. Now reset the fixture in the niche as outlined
The steps involved are
- Disassembling the Fixture
- Replacing the Bulb
- Reassembling the Fixture
Subsequent sections describes this process in
To remove the lens clamp, loosen the screws
that hold it in place. Gently pry the lens from the fixture. Do on
gouge the lens gasket.
Unscrew the old bulb, and screw in the new
one. Some fixtures contain a bare-coiled spring wire. It is not
wired to the electrical current and is designed to break the
circuit. If the bulb breaks while in use, the spring sweeps across
the filament, cutting the electricity in the circuit. This safety
item ensures that if water does get into the fixture, the next
swimmer does not get electrocuted.
Before reassembling the fixture, place it on
the deck and briefly turn on the light to make sure it works.
Normally a closed fixture is not turned on while out of the water.
With the lens off, however, the heat can escape.
To reassemble the fixture, simply reverse the
procedure described in previous sections. In addition, replace the
gasket. An old gasket has been exposed to months of chemicals, heat,
and compression. Place the new gasket around the lens as if it were
a rubber band stretched around a drinking glass. If the faceplate
screws into place, tighten the screws on opposite sides to apply
even pressure on the gasket and avoid gaps which later cause leaks.
Replace the fixture in the niche as described in Replacing a fixture
Designed like their 120/240-volt cousins,
low-voltage fixtures employ a transformer to drop the voltage to 24
volts. As a result, the highest wattage fixture does not deliver
much light, so they are used in spas or fountains where lower
wattage is sufficient to light a smaller area. Installation, repair,
and replacement techniques are identical to those described
The recent development in water lighting is
the use of fiberoptics. The hardware looks the same, but instead of
running electricity to a fixture, the cord in the conduit contains
thin plastic fibers that conduct light, not electricity. They
terminate in a lens in the water to shed the light into the pool or
spa. The light source and electricity are located safely away from
the body of water. Most of these are used in smaller bodies of water
because manufacturers have not yet developed fiberoptics with enough
power to light large pools. The manufacturers are working towards
development of the fiber optics light for large pools.
Troubleshooting and maintenance of low-voltage and fiberoptic
systems are similar to those described previously.
Electricity and water mix only too well, often
with deadly results. Therefore, since you can be injured or your
work might make you liable for someone else's injury, so be careful
when you are working on installing or replacing lights.
- If a fixture, lens, or gasket looks
suspicious, replace it. It's not worth the time, hazard, or
- Use the bulb, gasket, or replacement lens
that fits the fixture. Try to get the same manufacturer's
replacement parts or use the generic brand designed for that
make and model. You might be able to force a bulb, gasket, or
lens into place and it might stay watertight for a few days, but
what happens when it ultimately overheats and leaks, bringing
water, swimmer, and electricity into contact?
- Stubby bulbs are popular replacements. They
are squat, short bulbs so they fit almost any fixture. The
problem is that by being short, the heat is brought closer to
the end of the fixture than the originally designed long-stem
bulb. Also, bulbs with a reflector material painted on the
underside of the bulb will reflect more light into the pool, so
you get the appearance of a higher wattage bulb. The reflective
surface is also designed to direct heat away from the rear of
the fixture. This is significant because the resin at the rear
of the fixture, that makes it waterproof, can melt.
For the same reason, don't put higher wattage
bulbs in a fixture than it was designed to take. If it isn't marked
and you can't read the old bulb, don't use greater than 400 watts in
When changing a bulb, as with any repair, you
are required to work to local building and health department codes.
This might mean bringing an older installation up to code by adding
a ground fault interrupter (GFCI).
Replacing a bulb or fixture as outlined
previously is about all you will need to do with lights and water.
But how do you know if it's the bulb, cord, fixture, or breaker? if
the light won't come on, try this procedure.
- Make a visual inspection. Look at the lens
of the fixture (remove any color overlays first). If you can see
water or black soot (the result of a bulb bursting in the
fixture), you know it will have to come apart. If the water has
filled the fixture, it might only look cloudy, so it pays to
know what a dry, well-operating fixture looks like underwater.
- Turn off the power supply at the circuit
breaker. Open the J-box and expose the wiring connections. On
old J-boxes mounted in the deck, the gasket often fails and
allows water to fill the box. The water shorts out the wiring.
Clean and dry out the box and replace the gasket and lid firmly.
- If that is not the obvious problem, turn
the breaker and light switch on and use your multimeter to
verify that power is getting to the light fixture cord. if not,
trace back the problem to the breaker or switch. Sometimes there
is more than one switch, such as a remote control, and the
problem might just be a second switch being off.
- If the breaker trips off when you turn on
the light, disconnect the light cord from the power wiring at
the J-box and reset the breaker. If it still trips off, the
problem is the breaker or GFCI, or more rarely, the wires
between the breaker and J-box have shorted together. If the
breaker stays on, the problem is in the fixture or its wiring.
- Set your multimeter to test circuit
continuity. Touch one lead to the white wire of the fixture cord
and one to the black. If you have continuity, the bulb and
wiring are good.
- Touch one lead to the green and the other
to the white, then the black. If continuity exists between white
and green or black and green, the wiring is bad. You can test
bulbs that way too-touch one lead to the threaded part of the
bulb base and one lead to the tip of the base. A good bulb will
have a complete circuit (continuity), a bad one will not.
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