Water Heater Installation Basics

Last updated September 7, 2023
A knowledge of water heater installation is essential once you decide on the best water heater for your home. Proper installation ensures your water heater is connected to the supply lines and distributes water at the right temperature.
When installing a water heater make sure all manufacturing instructions are followed and local ordinances are met. This guide gives you the basics for installing a new water heater in your home.
Difficulty:
Advanced
Duration:
2-4 hours
Table of Contents
Get a Permit
Remove the Old Water Heater
Disconnect the Water Lines
Set Up the New Water Heater
Wrap the Heat Trap Fitting Threads
Replace Shut-off Valve
Get a Permit

A plumbing permit from your local building department may be required to install a water heater in your home. In some cases, an electrical permit may be required as well.
A mistake in installing or connecting the water heater could increase the risk of a fire, explosion or other hazardous conditions. The permit allows a local code inspector to examine the water heater installation and ensure that it is installed safely and properly.
Check with your local building department or code enforcement office before beginning your water heater installation project.
Remove the Old Water Heater

Installing a new water heater unit begins with the removal of the old heater. If you've got an electric water heater, replace it with another, unless you're willing and able to run gas line and exhaust vents. If you've got a gas hot water heater, stick with gas, unless your breaker box has room for a new 240-volt circuit.
- Turn off the water and gas supply valves and/or the power.
- Remove the electrical supply access plate at the top of the water heater.
- Check the connections with a continuity tester to make sure the power is off.
- Attach a garden hose to the drain valve and empty the tank.
- Using two pipe wrenches, disconnect the gas line at the union fitting if the pipe is galvanized or at the flare fitting if the gas supply line is copper.
- Cap the gas line to prevent any chance of a gas leak.
Disconnect the Water Lines

Whether the heat source is gas or electricity, make sure you shut it off before beginning work because of potential harm from flammables.
Electric water heaters can be shut off at the breaker box and may have an additional breaker closer to the heat pump. Gas and tankless water heaterswill have a cut-off valve, usually with a red handle, along the line leading to the hot water heater.
- Using two adjustable wrenches or pipe wrenches, disconnect the piping above the tank. If the piping or discharge pipe has been soldered into place, use a tubing cutter to cut it.
Set Up the New Water Heater

- Install the water heater in an area that leaves at least 6 inches of clearance around it for ventilation. Don't set it next to anything hot or flammable.
- Turn the water heater so that access to the burner and controls is unobstructed.
- Place a level on the side of the water heater and plumb it with plastic shims.
Wrap the Heat Trap Fitting Threads

- Use thread seal tape on the pipe threads. These fitting are directional and must be installed properly. Both have arrows showing the correct direction for installation.
- Attach the blue-coded fitting to the cold water inlet with the arrow facing into the water heater.
- Attach the red fitting to the hot water outlet with the arrow pointing away from the water heater.
- Tighten using two pipe wrenches or adjustable pliers.
Replace Shut-off Valve

If you've removed the shut-off valve, replace it. Here's how:
- Sweat solder the shut-off valve to the end of the cold water supply pipe.
- Use a MAPP torch and lead-free solder to connect the valve to the supply line.
- Solder with the valve in the open position to avoid overheating the parts.
Install the Water Relief Lines and Pressure Relief Line

Use an adjustable wrench to connect the pipe from the pipe run to the water heater.
- Turn on the main shutoff and open all line valves.
- Open all the faucets in the house and run the water in shower or bathtub until it flows steadily from them with the right water temperature.
- Close the cold and hot water faucet.
Now that you know the basics about water heater installation, you can decide whether the project is for you. When you're ready to purchase the water heater and tools you need, download The Home Depot Mobile App to buy the supplies from the inventory.
Tip: The Home Depot highly recommends that you hire a professional for water heater installation. Trusted pros are available for same-day installation when you call before noon in most areas. Schedule an appointment today.