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How to Install an Electric Water Heater

Install a new electric water heater to save money and energy. Our video and step-by-step guide shows you how.

Before You Begin

Determine whether you need to replace your water heater or if maintenance will suffice.

If you’re not getting hot water, it could be the heating element or another maintenance issue. Take a quick maintenance assessment before embarking on a full replacement.

If you have water on the floor or on top of the unit (this is different from water leaking from a supply line above the unit), you’ll probably need a new water heater. The data plate on your current tank has size and energy specifications that help make buying a comparable unit easier. If your family has grown larger or smaller, this is a good time to consider upsizing or downsizing your water heater. 

Check local building codes before you get started to ensure compliance. If you’re not comfortable, call a pro.

Caution

Only use piping, sealants and solder suitable for potable water when working with water-using appliances.

Water Pressure

Pressure gauge attached to a hose at an outdoor spigot to determine the home's water pressure.

Check your home’s water pressure using a pressure gauge on your outdoor spigot. 50-60 PSI is ideal. If your home’s water pressure is greater than 80 PSI, lower it with the pressure-reducing valve at the main water shut-off. If your home doesn’t have a pressure-reducing valve, a professional can install one for you.

Your home’s water pressure is important for all water-using appliances. Reduced pressure lessens stress on plumbing lines and extends the life of appliances and fixtures.

You might want to consider an inline pressure gauge for pressure monitoring.

Expansion Tank

Expansion tank installed on supply line with push-fit fittings.

Determine which expansion tank you will need. A thermal expansion tank alleviates excess pressure in the lines of a closed system. A 2-gallon expansion tank works with water heaters up to 50 gallons. A 5-gallon expansion tank is needed for water heaters up to 100 gallons. Check the manufacturer’s recommendations for exact sizing.

The expansion tank installs to the cold-water supply line near/above your water heater. You can install an expansion tank using push-fit fittings. They slide into the pipe -- no soldering is needed. If you decide to solder, de-burr and clean pipes and fittings. Apply soldering paste and assemble. Heat the fitting and solder.

The expansion tank pressure must match the main water pressure to work effectively. Use a hand air pump to increase pressure or depress the valve to lower it.

Removing the Old Water Heater

Step 1

Wires labeled with masking tape for reconnection reference.

Turn off the electricity 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.

Step 2

Garden hose attached to tank drain to empty old water heater.

With the water supply still on, turn a 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.

Step 3

Faucet with hot water open to drain the water heater tank faster.

Open the drain valve and empty the water heater into buckets or down a drain. Sometimes opening a hot water faucet on a sink helps the water heater tank to empty faster.

Step 4

Disconnecting the discharge pipe with a wrench.

When the tank is empty, remove the discharge pipe from the T&P (Temperature & Pressure) 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.

Good to Know

You may reuse the dishcarge pipe. Do NOT reuse the T&P relief valve.

Installing the New Water Heater

Caution

Water heaters are heavy - use a helper, appliance dolly or hand truck when moving the appliance.

Step 1

PEX pipe running to drain to prevent leaks from the drain pan.

Place the new water heater in a drain pan. You can avoid possible flooding by routing pipe to a drain from the drain pan.

Step 2

Temperature and Pressure valve in the side of an electric water heater.

If your water heater did not come with a new T&P relief valve pre-installed, simply twist in the new valve now. It may be in the box or you may need to buy your own. Do NOT reuse the old valve. The T&P valve automatically opens if the temperature or pressure becomes too high for the tank.

Good to Know

Before you buy, note the stem length required by your water heater model.

Step 3

Discharge pipe from T&P valve running into a bucket that will catch run-off.

Install the discharge pipe from the T&P relief valve toward the floor or drain. If there is no drain underneath the pipe, put a bucket underneath to catch water dripping from the discharge pipe. Cut the pipe so it is no more than 6 inches above the bucket.

Caution

Only use copper or CPVC pipe for T&P discharge.

Step 4

Plumbers tape on threads.

Use a flexible hose kit for water hook-up. Apply plumber’s tape to the threads of the heat trap nipples. Then, attach the hoses.

Step 5

Dielectric fittings.

Some areas require dielectric fittings to reduce corrosion between two different metals. Your area’s local codes and ordinances should detail the specifics of installation in your area.

Step 6

Hose held against the pipe with a little slack.

Apply plumber’s tape to one end of a connector body threads. Secure the fitting to the hose, and then hold the hose up to the pipe. It should have a little slack. Mark and cut the pipe, removing any burrs.

Step 7

Sliding the compression nut on the pipe with the fitting on deck.

Slide the compression nut and ring onto the pipe. Push the pipe into the fitting and tighten the nut.

Step 8

Illustration with of water heater secured to the studs with seismic straps.

Some areas require seismic straps to prevent earthquake damage. These straps brace the water tank against the wall to keep the unit from toppling over. If you’re not in an earthquake zone, skip ahead to the next step.

Seismic straps should be installed approximately 6 inches from the top of the water heater and 18 inches from the bottom. Locate the wall studs closest to the strap measurement and drill pilot holes.

Secure one end of the strap to the stud with a socket and ratchet. If block covers the studs, use a masonry bit to create a pilot hole. Wrap the strap around the water heater and adjust the size, securing the adjustable bracket on the opposite side.  Pull the strap tight and repeat the process on the lower strap.

Caution

Defer to the manufacturer’s instructions for seismic strap installation.

Step 9

Hand touching the water connections to check for leaks.

To fill the tank, remove the aerator from the nearest faucet and open the hot side. Slowly turn on the water supply and check connections along the water heater for leaks. If you are 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.

Step 10

Spurting water coming from faucet to clear air in the tank.

When water runs from the faucet, the tank is full. Let the water run for three minutes to empty air and debris out of the tank.

Caution

The tank must be completely full before connecting the wiring to avoid dry firing – which ruins the heating element.

Step 11

Removing cover plate with a screwdriver.

To connect the wiring, remove the junction box cover. Attach the ground wire to the green ground screw. Use your masking tape connection notes as a guide. Twist the wires together with wire connectors.

Step 12

Replace the cover plate after connecting wiring.

Replace the junction box cover and turn the power on at the circuit. If your new water heater does not have power, turn the circuit off and check the connections.

Step 13

Temperature control knob set to 120-degrees.

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

Step 14

Reducing pressure with a wrench.

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.

Caution

Water coming from the discharge pipe may be hot.

Step 15

Removing the aerator from a faucet clogged by debris from the new water heater.

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.

Preventing Scalds

Even with the temperature gauge set to 120 degrees, scalds are still a concern. Children, older people and those with sensitive skin are especially at risk. To prevent injury, consider installing thermostatic mixing valves.

Installed at the point-of-use faucet, fixture or appliance, a thermostatic mixing valve controls both the volume and temperature of water by attaching to both the hot and cold water supply. The settings may be adjusted inside the valve itself to provide optimum comfort.

Step 1

Turn the water supply off and use only materials (tape, pipe, solder, etc.) that are safe for potable water (because the water may be ingested).

Step 2

Solder the connections to the valve before attaching to the plumbing. Connect the valve to the hot and cold water supply and the outlet pipe. If additional soldering is needed, maintain a safe distance from the valve because excessive heat may cause damage.

Step 3

Turn the water supply on to test for leaks. Tighten and correct as necessary. Follow the manufacturer’s instructions for adjusting water temperature.

Caution

Defer to the manufacturer’s instructions for installing a thermostatic mixing valve.