How to Install a Gas Water Heater (DIY)

Posted by James Memije on Sep 23, 2015 9:59:00 AM
James Memije
So, you've decided you want to replace your water heater yourself. It may seem like a daunting task, but with the right knowledge and tools, you'll have your new system up and running in no time! 

Gas water heaters require a gas supply, a cold water supply, and a flue connection to carry away harmful gases. Today's homes tend to be airtight, so make sure you have adequate venting before starting a gas water heater installation. Carbon monoxide, a byproduct of combustion, can be fatal when inadequate venting allows it to build up in the home. When installing your water heater, make sure to follow model-specific information, warnings, safety notices, and local codes.

Here, we’ll walk you through how to successfully plan for and install a gas water heater yourself! water-heater-installation-toronto

Start With a Plan

Make Important Decisions

1. Choose a gas water heater brand.

2. Determine if you want a PV or conventional water heater.

3. Ensure you have a gas supply; if you don't, you need to figure out how you'll get it. Whether that involves running a supply line from your main line or, if your home doesn't have it to begin with, getting the city to supply you with a gas meter. Running a gas line is difficult and dangerous if not done correctly, so you may want to hire a contractor for this.

4. Determine how the gas water heater will be vented. Conventional will be vented through your chimney while a PV will use a PVC and go through the side of your home. For the PVC route, determine the path through which the venting will go, and if you have any finished walls or ceilings, your bulkheads will have to be opened up.

5. Electrical (for PV) - Determine how you will supply 110V for the venter motor. You may want to contact an electrician.

6. For a new install, ensure your hot water and cold water supply is at the location of new tank. We highly advise that you hire a plumber for this step to help you determine if you need a mixing valve or not.

What do you need for this DIY installation?

You’ll need common plumbing tools and pipe joint compound approved for fuel gas.

All the tools you’ll need:

Electrical tape
Plumbers tape
Safety glasses
Pipe wrench
Soldering torch
Tape measure
Tube cutter
Voltage tester
Wire stripper/cutter
4-in-1 screwdriver
Adjustable wrench


All the materials you’ll need:

Water and gas piping
Mixing Valve
Pipe thread compound
Venting pipe and connectors


You’ll also need leak detection solution, or you can use children’s soap bubbles or hand-dishwashing soap mixed with water.

Most codes require the water heater to be installed in a metal drain pan. Refer to the installation instructions for information about sizing the drain pan and other installation details.

If your house has copper pipes, consider an installation kit with compression fittings that don’t require soldering. If your pipes are plastic, you’ll need connectors/fittings for the specific type of plastic pipes used in your home. Read the installation instructions for the new connectors before cutting the existing water pipes.

Before you start, turn the main gas supply valve off. Also, turn the gas control knob on the old water heater off. Open a hot-water faucet and let the hot water run until cool. Allow the old water heater and vent pipe to cool.

DIY Installation Steps

After you’ve purchased all of the necessary components, you’re ready to start installing. Here are the appropriate steps to take for a safe and successful gas water heater installation:

1. Drain Your Existing Water Heater

a. Turn off the water and gas supply.

b. Attach a garden hose to the drain valve and empty the tank.’

c. Turn on a hot water faucet to allow air into the system.

2. Disconnect the Gas Line and Water Lines 

a. Disconnect the gas line 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.

b. Using two adjustable wrenches or pipe wrenches, disconnect the water lines above the tank. If the piping has been soldered into place, use a hacksaw or tubing cutter to cut the pipe. Make sure the cuts are straight.  

3. Detach the Gas Exhaust from the Flue Hat 

a. Remove the screws connecting the vent to the water heater using a screwdriver or nut driver.

b. Remove the old water heater – you may require help for this because older water heaters may tend to fill with sediment and are heavier than new ones.   

4. Set the New Water Heater in Place

a. Install the water heater in an area with at least six inches of clearance around it for ventilation. Also, make sure to place the water heater so there is unobstructed access to the burner and controls.

b. Place a carpenter's level on the side of the water heater and level it with plastic shims if necessary.

c. Reconnect the flue hat to the gas exhaust vent.   

5. Install the Heat Trap Fittings 

a. Wrap the water heater heat trap fitting pipe threads using teflon tape. These fittings are directional and must be installed properly. Both have arrows showing the correct direction for installation.

b.  Attach the blue-coded fitting to the cold water inlet with the arrow facing into the water heater.

c.  Attach the red fitting to the hot water outlet with the arrow pointing away from the water heater.

d. Tighten using a pipe wrench or adjustable pliers.  

6. Install Water Line Connections

a. Measure and cut the water line connections to length.

b. Reconnect the water line

7. Connect the Gas Supply Line 

a. Before connecting the gas line, clean all threads with a wire brush and rag.

b. Apply piping compound to the threads of the black pipes as you connect them. Assemble and tighten each fitting with two pipe wrenches.

c. Install the union fitting last because it connects the new line to the existing line. When finished, open the gas supply valve and turn the water on.

d. Turn on water at the tank, and then turn on one or more hot water faucets to bleed air out of the system once the water is turned on at the tank.  

8. Test the Gas Line for Leaks 

a. Fill a sponge with a mixture of liquid dishwashing soap and water, and apply it to the new fitting – check for bubbles.

b. Test all connections - if there's a leak, bubbles will form on the surface and you'll have to refit the joint.   

9. Light the Pilot

a. Remove the burner access panel.

b. Turn the knob on top of the control box to the “pilot” position.

c. Hold a lit fireplace match or barbecue lighter to the pilot access opening.

d. Press and hold down the reset button on the control box for 60 seconds after the pilot ignites.  

10. Turn the Control Knob to the "On" Position

a. Turn the knob on top of the control box to the “on” position - you should hear the burner ignite. If it doesn't, remove the access panel and relight the pilot.

b. Replace the burner access panel and set the control at 118 to 123 degrees F.

c.  Allow water to be heated for several hours.

And there you have it. These detailed strategies and instructions will help you install a new gas water heater yourself – not to mention save energy and money while staying safe. DIY never felt so comfortable! 

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Topics: Water Heaters

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