Installing Underwater Illumination
The demand for outdoor living enhancements is growing every year. Water features are popular
additions to outdoor living spaces. Lighting these features can be challenging — yet rewarding.
The most common way contractors illuminate water is by using a submersible fixture.
Low voltage underwater fixtures come in several different varieties. Adjustable
projection-style fixtures are designed with integrated light sources or a drop-in lamp such as an
MR16, MR11, or PAR36. Onmidirectional style fixtures use miniature drop-in lamps such as a G4
bi-pin, single contact bayonet, or a built-in LED light source. Both styles of fixtures usually come
with a weighted base and a two or three-conductor SO- style cable.
Adjustable projection-style fixtures are very effective when illuminating a waterfall or the
underside of a tiered fountain. These fixtures can also be used to illuminate the water flow in a
stream. Illuminated moving water creates a dramatic effect on any surrounding architecture or
plant material on a property.
Omnidirectional fixtures can be used underneath a waterfall to create a backlighting effect. When
placed in the bottom of a pond, an omnidirectional fixture can provide soft, even illumination.
Depending on the viewing angle, this type of fixture may need to be shielded with underwater
plants or flat rocks.
When selecting an underwater fixture, be aware of the clarity and depth of the body of water. A
murky pond will not look any better with a light in it. If the water is deep, you may need to use a
brighter lamp or a narrow beam angle to project the light through the depth of the water.
Many mistakes can occur when installing a low voltage underwater fixture. The most common is
in the cable connection.
· Round SO cable is normally used on most submersible lighting fixtures.
o This is a multi-conductor style cable that contains fiber spacers between the
· Proper sealing of the cable ends is very important.
o The fiber spacers can act as a wick and allow water to be drawn into the fixture.
· A best practice is to ensure the connections are made away from the water and in a dry
· If the fixture must be spliced underwater, use a UL-approved submersible junction
box or epoxy filled cable connector.
Always be sure the transformer used on a project is approved for underwater lights; confirm this
on the manufacturers’ website. When servicing an underwater fixture, it is critical to change the
seal every time you service the fixture.
And finally, be sure to read all the specifications on the chosen underwater lighting fixture. Many
of these fixtures are not made for “people water,” like swimming pool waterfalls or splash pads.
Check with a local electrical inspector for any special requirements pertaining to the installation of
underwater fixtures. Inspectors may require that fixtures be bonded to the control panel, even
though the fixtures are low voltage.
The effects of underwater lighting can be quite stunning. Follow these guidelines and keep it safe