How to Replace and Install an Electric Water Heater

Learn how to install an electric water heater properly. What is the right location for the new unit? Instructions on how to remove an old electric heater and when is the right time to do so. Is the heater installation considered a DIY project, or does it have to be done by a professional?

Before shopping for a new heater

Electric water heater

If your old electric water heater is not working correctly, there is not enough or no hot water, recovery and efficiency are extremely low, check out this troubleshooting guide. The guide can help you fix the problem and avoid costly purchase.

Check the simple things first, such as the tripped breaker or reset button, or is there a power supply at all. Be aware that something series might be going on as well.

However, if your old unit is leaking, water has a rusty look, the tank is deformed, performance is still low after the repair, you might want to consider buying and installing a new electric water heater.

Things to consider

If your older heating system didn’t include the expansion tank and pressure relief valve, now is the time to install it.

Expansion tanks are used in closed water heating loops to reduce the water pressure buildup when it gets higher than usual, protecting the heater’s elements.

Pressure relief valves are also recommended in homes where the water pressure inside the plumbing varies. The recommended pressure ranges from 50 to 60 PSI, while everything above 80 PSI requires you to install a valve, therefore avoiding potential problems.

Standard electric water heaters with two heating elements operate on 240V, which requires breakers and a wire gauge set by the manufacturer (usually a 30-amp circuit breaker and 10-2 wire with the ground). Make sure that the correct voltage is supplied to the heater, as stated on the rating plate.

Recommended fuse size chart

Watts 120V 208V 240V
600 10A 5A 5A
750 10A 5A 5A
1000 15A 10A 10A
1250 15A 10A 10A
1500 20A 10A 10A
2000   25A 15A
2500   30A 15A
3000   35A 20A
3500   25A 20A
3800   25A 25A
4000   25A 25A
4500   30A 25A
5000   35A 30A
5500   35A 35A
6000   40A 35A

Note: Always follow the manufacturers’ manual for instructions. Check local building codes and get all the necessary permits.

If you are not sure how to install an electric water heater or have problems during the replacement, contact a professional plumber to help you.

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How to remove an old and install a new electric water heater

Required tools

  • Multimeter (voltage detector)
  • Set of screwdrivers
  • Adjustable wrench
  • Pliers
  • Tubing cutter (if using copper pipes)
  • Torch (if using copper pipes)
  • Soldering flux and solder wire (if using copper pipes)
  • Wires and wire nuts
  • Garden hose
  • Bucket
  • Teflon tape (pipe dope)
  • Earthquake straps (where required)


  • Turn OFF the power on the electric panel box.
  • Locate the junction box on the top of the heater.
  • Use the multimeter and put the probes on the wires of the heater to confirm that the power is off.
  • Remove the conduit from the tank.
  • Open the nearby faucet to reduce the pressure and temperature of hot water stored inside the tank.
  • Turn off the water supply to the tank on the nearby shut-off valve. 
  • Locate the drain valve at the bottom of the heater.
  • Drain all the water from the tank by connecting one end of the garden hose to a drain valve and the other end to the nearby floor drain, or outside. If the water cannot drain, the drain valve could be plugged with the sediment buildup. Use this article to learn how to remove the sediments.
  • To speed up the process, open the faucet or T&P valve.
  • Locate the T&P valve at the top of the heater and remove the discharge pipe from it.
  • Disconnect the cold and hot water supply pipes located at the top of the unit.
  • Remove the old tank. Use a dolly for this job.
  • Install a drain pan if one didn’t exist before. You can also put the heater on the concrete blocks to protect the unit from floods and make draining easier.
  • Set a new water heater in the drain pan or on the platform.
  • Install a discharge pipe on the T&P valve. The pipe must provide unobstructed water flow to the drain and end approximately 6” from the floor. For the same purpose, you can use a bucket.
  • Install a new cold water inlet (blue ring) and a hot water outlet (red ring). To make the process faster and avoid time-consuming when soldering the copper pipes, use flexible steel pipes, SharkBite Push-to-Connect or PEX tubes.
  • Use the Teflon tape on the threads, where required, to avoid leaking. You can also combine it with the pipe dope securing the connection. Use dielectric fittings if needed to prevent corrosion.
  • Turn on the cold water supply.
  • Open the hot water tap.
  • Check all connections for leaks.
  • Once the tank is full, you will see water coming out in the steady stream.
  • Let it run for a few minutes to bleed the air from the system.
  • Remove the junction box to free the electrical wires.
  • Connect the wiring using the wire nuts.
  • Turn the power on, on the breaker box.
  • Depending on the wattage of the heating elements and the size of the tank, it could take several hours to heat all the water. 
  • While the thermostat is usually factory set to 120-125 F, set the temperature to your needs, but avoid higher temperature due to scalding. You must expose the thermostats as they are located behind the access plates and insulation.

Note: A water heater tank must be full of water because if you turn the heater on too early and if the heating element is not submerged into the water, you might get a dry firing which will destroy the component.

Related: How to install a gas water heater


If installing an electric water heater in the new house, it is vital to choose the location wisely.

The best location for the water heater is close to the point of service, electrical, and plumbing supply, and where it cannot damage the area or hurt people due to leaking or unit malfunction.

Avoid storing flammable materials in the same room as the heater.

Since the electric heaters are built for indoor use, you still have to protect them from freezing if exposed to a lower temperature (use the insulation blanket and pipe sleeves).

The unit should be sitting on the floor in the vertical position with all the controls and drain accessible for maintenance, replacement, and service.

How does an electric water heater work

An electric water heater is a simple device that is used for heating potable water. Cold water from the home plumbing enters the storage water tank, where it is heated with the heating elements.

Cold water enters the tank through the inlet tube (marked with the blue ring), called a dip tube, and exits through the hot water outlet (marked with the red ring). Water is then heated with one or two electric resistance elements and delivered to the shower or fixture (point of use).

Every heating element has a thermostat that turns it on when the inside water temperature drops below the set one.

Related: How to install a heat pump


As shown in the above text, electric water heater installation is not a complicated project, especially for DIYers with the right tools. Basic to intermediate knowledge of the electrical and plumbing work is required.

Keep in mind that new electric heaters usually last 10-15 years, so no matter if the heater is old, or it started to malfunction, try to fix it first, or at least call a plumber to check it out, and only if it is not worth repairing, get a new one.

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