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Pond lighting

How to light a pond and waterfall at night

How to light a pond and waterfall at night

Light a backyard pond with 12 volt LED fixtures run from an outdoor transformer that plugs into a GFCI outlet. Put the brightest light under the water at the base of the main falls, pointed away from where people sit, and add a small light at each lower drop. Then add up the fixture watts and buy a transformer with headroom: The Pond Guy says to use 90 percent of its rating, and the landscape lighting maker VOLT says 80 percent. Keep the cable runs short enough that the last light gets the same voltage as the first, and put the whole system on a photocell with a timer.

What the manufacturers and the electrical code say

The sources agree on how to size the transformer and differ on the margin. The Pond Guy writes that "Most pond lights use 12-volt power" and "We recommend using only 90% of the transformer output to maximize light potential." VOLT Lighting tells its customers to "Multiply the transformer's wattage by 0.8 to find its usable capacity (this keeps the recommended 20 percent buffer)." Aquascape's light manual gives no percentage. It says the lights are "designed to operate on a 12-volt, outdoor-rated transformer," that running them outside "the 9-15 volt operating range voids the product warranty," and that "It is recommended to locate the transformer as close to the light fixtures as possible to avoid voltage drops caused by long cable runs."

The same manual lists what each light draws, which is the number you add up.

Aquascape pond and landscape LED lights, from the manufacturer's spec chart
LightWatts drawnLumensColor temperatureBeam spread
1-watt waterfall light1.2453,000 K30 degrees
1-watt spotlight1.2453,000 K30 degrees
3-watt spotlight31503,000 K30 degrees
6-watt spotlight5.83403,000 K30 degrees

Voltage drop depends on the cable gauge, the run length and the total watts on that run. USA Light, a lighting manufacturer, publishes a chart for a 12 volt transformer that keeps at least 10.5 volts at the fixtures; on 12 gauge wire, "When you increase the load to 100watts your wire run should not exceed 65 feet." VOLT uses a simpler rule: multiply the watts on the run by its length in feet, use 12 gauge if the result is 10,000 or less, and use 10 gauge or split the run into two zones if it falls between 10,001 and 15,000.

Longest cable run by load and gauge, from USA Light's chart and VOLT's watts-times-feet rule
Watts on the runUSA Light, 14 gaugeUSA Light, 12 gaugeUSA Light, 10 gaugeVOLT, 12 gaugeVOLT, 10 gauge
50 watts81 feet129 feet204.5 feet200 feet300 feet
100 watts40.6 feet65 feet102 feet100 feet150 feet
150 watts27 feet43 feet68 feetabout 67 feet100 feet
300 watts13.5 feet21.6 feet34 feetabout 33 feet50 feet

For the GFCI question, the National Electrical Code treats a pond as a fountain. In the 2017 edition, section 680.2 defines a fountain as "Fountains, ornamental pools, display pools, and reflection pools," and section 680.50 applies Part V "to all permanently installed fountains." Section 680.51(A) says that luminaires and submersible pumps, "unless listed for operation at low voltage contact limit or less and supplied by a transformer or power supply that complies with 680.23(A)(2), shall be protected by a ground-fault circuit interrupter." The low voltage contact limit is 15 volts RMS for ordinary AC, and a transformer that meets 680.23(A)(2) has to be "listed, labeled, and identified for swimming pool and spa use." Section 680.58 adds that receptacles "located within 6.0 m (20 ft) of a fountain edge shall be provided with GFCI protection." Aquascape's transformer manual says its units "should not be used with either swimming pools or spas," and tells the installer to "Plug transformer into GFCI outlet." Check which code edition your town has adopted. Either way, the outlet the pond transformer plugs into should be GFCI protected.

On timers, the Aquascape Quick-Connect Photocell with Timer "automatically turns lights on at dusk," then turns them off at dawn or after its "4-hour, 6-hour, and 8-hour settings," and it is rated "Up to 60-Watt capacity." On color, every light in Aquascape's chart is 3,000 K, and DarkSky's lighting principles ask for "warmer-color lights where possible" and "controls such as timers or motion detectors."

What contractors and retailers do

Benjamin Timmermans of Liquid Landscapes, writing in POND Trade Magazine in 2017, says "I always use higher wattage at the base of waterfalls so the light can travel through the descending waterfall, creating a primary focal point," that fixtures in a pond should go "at varying depths and angles," and that "less is more." He warns against "direct light shining into viewers' eyes."

Webb's Water Gardens describes two approaches, with some owners using "one spotlight at the base of a waterfall as a main focal point," and adds, "If you have a waterfall with drops, you may also want a small light in each of those areas to illuminate that cascade." Premier Ponds of Glenwood, Maryland, says to "Place small submersible LED lights behind or beneath waterfalls to light up the falling stream," and its heading on aiming reads "Don't Shine Lights Straight Up." Aquascape Construction of St. Charles, Illinois, puts "a waterfall light behind a cascade," and Meyer Aquascapes of Cincinnati describes uplighting as lights "positioned at the base of water features or along the pond's edge to cast their glow upward."

The practitioners disagree on how hard to load a transformer. Premier Ponds writes that "a 60-watt transformer can handle ten 6-watt lights or twenty 3-watt fixtures," which is a full 100 percent load, while The Pond Guy stops at 90 percent and VOLT at 80 percent.

Where the sources differ and why it matters

The two voltage drop rules give different run lengths because they assume different lamps. USA Light's chart holds the fixtures at 10.5 volts. VOLT says its "LED lights work from 8V to 15V," which gives "much more freedom in how you wire your yard compared to older halogen systems," and Aquascape rates its lights from 9 to 15 volts. That is why VOLT allows 100 feet of 12 gauge at 100 watts where USA Light allows 65 feet. If any halogen fixtures share the run, use the shorter column.

The top of the range matters too. USA Light sells transformers with 13, 14 and 15 volt taps for long runs and says to check the first fixture "and make sure it does not exceed 12volts." Fifteen volts is the top of Aquascape's rated range and also the code's low voltage contact limit, so meter any run fed from a high tap.

No manufacturer we found publishes a number of lights per foot of spillway or per drop. The advice to put a light under each drop comes from retailers and contractors, so treat it as a design choice you can adjust to the falls you have.

What to do

  1. Decide what deserves light at night: the main falls, one or two drops, and one or two plants or boulders. Leave the rest dark. The Pond Guy says to shine the light on the pond rather than toward the patio, with waterfall lights "pointing away from the viewing area."
  2. Set the brightest underwater fixture at the base of the main falls, aimed up into the falling water at an angle away from the seating area. Add a 1 watt light under each lower drop if you want the cascade to read as a series of steps.
  3. Add up the watts. For a 3,000 to 10,000 gallon pond with a three-drop waterfall, two 6-watt spotlights draw 11.6 watts, three 1-watt waterfall lights draw 3.6 watts and two 3-watt landscape spots draw 6 watts, for 21.2 watts in all. At The Pond Guy's 90 percent, that needs at least 23.6 watts of transformer (21.2 divided by 0.9), and at VOLT's 80 percent it needs at least 26.5 watts (21.2 divided by 0.8). Aquascape's quick-connect transformers come in 6, 20 and 60 watt sizes, so this plan goes on the 60 watt unit, with room to add lights later. A 1,000 gallon pond with one 6-watt spot and three 1-watt lights draws 9.4 watts and fits a 20 watt transformer under either rule. A 20,000 gallon pond often needs several runs, and then the voltage drop table decides the gauge.
  4. Check the longest run against the table. A load under 50 watts on 12 gauge stays inside USA Light's 129 foot limit, so most pond runs are fine when the transformer sits near the pond.
  5. Plug the transformer into a GFCI-protected outdoor outlet. If the outlet is not GFCI protected, have an electrician install one before the lights go in.
  6. Coil extra cord at each underwater light so it can be lifted out for cleaning; section 680.51(F) says fountain equipment "shall be removable from the water for relamping or normal maintenance." Keep the quick-connect fittings out of the water, since Aquascape warns "Do not submerge quick-connect fittings."
  7. Fit the photocell, set it to turn off after 4, 6 or 8 hours or at dawn, and walk the yard after dark to re-aim anything that throws glare toward the house.

Underwater lights and uplights do different jobs. A light under the water shows the falling water and the fish, and a spotlight on a stake at the edge lights the rocks and plants. Aquascape's spotlights come with both a stand and a landscape stake, so one fixture can do either. The Pond Guy says underwater lighting "is best installed when your pond is empty," during construction or the spring cleanout. For the flow over the falls you are lighting, see how big a pump a waterfall needs, and for the layout of the drops themselves, how to build a pond waterfall and stream.

Previewing the night view

The PondTools studio renders the pond, rock and waterfall in 3D on the client's own yard at any presentation time from 6:00 in the morning to 11:00 at night, so you can show the design after dark and agree on which features to light before any cable is buried.

Sources