How to Install an Electric Water Heater

Turn off the electricity to the water heater at the circuit breaker. Use a circuit tester to make sure the power is off. Use tape to mark the wire connections and disconnect the wires by removing the wire connectors.

With the water supply still on, turn a nearby faucet on hot and let it run until the water is cool. Shut off the cold-water supply line and connect a garden hose to the drain valve on the bottom of the water heater. Open the drain valve and empty the water heater into buckets or down a drain.

When the tank is empty, remove the garden hose and discharge pipe from the temperature and pressure (T&P) relief valve. Disconnect the water supply lines. If you must cut them, leave them as long as possible. Have someone help you remove the old tank with a hand truck.

Place the new water heater in a drain pan. Drain pans are made from plastic, aluminum, galvanized steel or stainless steel. Your drain pan should be at least two inches wider than the diameter of your new water heater. It should be between 1-1/2 to 2-1/2 inches in depth. Local building codes may specify the type and size of the drain pan that is required. Also, leave at least 6 inches of clearance around the heater for ventilation.

You can avoid possible overflow by routing a pipe from the drain pan to a drain. Check to make sure the drain pan connector is the correct type of pipe you are using, either PVC or CPVC. Lay out your new drain lines along where the old lines are so you can measure, cut, prime and glue them in place.

If your water heater didn't come with a new T&P (temperature and pressure) relief valve installed, simply twist in the new valve now. The T&P valve automatically opens if the temperature or pressure becomes too high for the tank. It may be in the box, or you may need to buy your own. Don't reuse the old valve.

Position the runoff tube from the T&P relief valve toward the drain pan or drain. Cut the tube so it's no more than 4 inches above the floor. Apply some Teflon tape and pipe glue to the threads. Attach the tube into the valve, hand tightening until it is snug. If there's no drain pan or drain underneath the tube, put a bucket underneath to catch any water dripping from the runoff tube.

Many of today’s new water heaters come pre-equipped with dielectric water fittings for the hot and cold supplies. These fittings are designed to reduce corrosion between two different metals. Apply thread tape and sealant to the fittings before attaching any supply lines.

Before connecting the water supply, you should install a thermal expansion tank. Expansion tanks are designed to protect your water heater, appliances and fixtures from excess water pressure and avoid “water hammering,” which is the noise in the lines as the water is heated.

Expansion tanks can be placed just above the water heater supply intake or along the water supply line. For this example, connect the T fitting to the intake fitting and tighten with your adjustable wrench. Next, remove the air valve cover and measure the tank’s air pressure with your air pressure gauge. You want the tank pressure to match your home’s water pressure that you measured previously. Many tanks come pre-charged at 40-PSI. Check the tanks’ pressure and add air with your manual air pump if necessary to match your home’s water pressure. Thread the tank onto the T fitting and tighten. Add a connection fitting to the open T fitting for the water supply line.

Now you can attach the water supply lines. Premade supply lines are very handy as they come already assembled with fittings, rubber gaskets so you don’t need tape, push to fit pex connections and a shut-off valve. Simply attach the threaded end to the fitting on the T that you just installed and tighten.

Next, bend the supply line up and measure to the old cold water supply line. If you need to trim the old line to make a straight connection, use a pipe cutter to make a clean cut and then deburr the end. The deburring tool can also help mark the connector depth. Push the connector onto the hose to the mark. Repeat the process for the hot water (red) side and tighten all connections.

Make sure the in-line shut-off valve just above the water heater is closed. Remove the aerator from the nearest faucet and open the hot side. Turn on the water supply at the main valve and slowly open the in-line valve. Check connections around the water heater for leaks. If you're leak free, fill the tank. If you have leaks, shut off the water supply and gently tighten the connections. Repeat until the connections are secure. When water runs from the faucet, the tank is full. Let the water run for three minutes to flush the tank and empty air and any debris that may be inside the tank and lines.

Use your masking tape connection notes as a guide for making your electrical connections. Attach the ground wire to the green ground screw by forming a small hook in the wire. Next connect the black and red wires with those on your new unit. Wire connections will be two hot wires and one ground wire. Twist the wires together with wire connectors.

Once the connections have been made, place the wires into the electrical compartment and secure the remaining cover. Return to your breaker box and turn the power to the unit back on. If your new water heater doesn't have power, turn the circuit off and check the connections.

Follow the manufacturer’s instructions to set the temperature to 120 degrees Fahrenheit. It may take several hours to initially heat the water.

After a few hours, check the discharge pipe that runs out of the T&P relief valve. A dripping pipe usually means the pressure is too high. Turn the pressure down below 80-PSI.

If a faucet stops running after installation, remove the aerator from the faucet in question and let the water run for a few minutes to clear loose sediment. Rinse and replace the aerator.

Replacing a water heater may seem like a complicated job. But by taking your time and following the directions, it can be a do-it-yourself friendly project. Still unsure or don't have time to do this project yourself? Check out our professional water heater installation service.