How to Install a Small Water Heater Under a Kitchen Sink

Hold the compact electric water heater in place on the back wall under the sink. Mark the location of its mounting holes on the wall using a pencil or pen. Drill pilot holes at each mark. Fasten the unit to the wall, using the manufacturer's supplied mounting screws or bolts.

Wire the water heater directly to its own breaker using three-wire UL-approved 8-gauge insulated wiring. Leave the breaker in the "Off" position until you complete the installation. Attach the color-coded wires to the proper electrical terminals located inside the water heater. Like an electric stove, under-sink tankless water heaters designed for kitchen use will require a 240-volt service line.

Feed a plumbing line to the water heater's inlet using copper piping. Attach the pipe end to the supplied compression fitting. Tighten the fitting in place at the inlet connection, using a wrench or channel-lock pliers. Do not use solder or teflon tape.

Run a plumbing line from the water heater's output connection directly to the hot water fitting of the faucet. Attach the pipe end to the supplied compression fitting. Tighten the fitting to the water heater output connection, using a wrench or channel-lock pliers.

Flip the breaker to the "On" position and turn on the water main.

Test the water heater by turning on the hot water at the sink and running hot water for five minutes. Check for leaks at the input and outlet valve. Adjust the temperature to your preferred level by using the water heater's thermostat.