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Gas Water Heater Installation: Step-by-Step Directions to Do It Yourself


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Gas water heater installation may seem like a job for the pro's, but actually, it's not as difficult as you may think. Certainly, the easiest way to get the job done is to hire a professional to do the work for you. However, if you want to save a little money and achieve a feeling of accomplishment, installing your gas water heater is a great DYI project.

When selecting a new water heater, it's generally best to stay with the same fuel type (gas or electric) unless there's good reason to switch. It's also a good idea to check with a local plumbing inspector. They can share the local plumbing codes with you, as well as let you know if you'll need a municipal permit.

Another point to consider is how to dispose of your old water heater.  If you hire a professional you won't need to worry about this because they will haul your old water heater away for you. Still, if you enjoy doing projects yourself, and you would like to save yourself some money, replacing a gas water heater is not hard.

Preparing to Install a Gas Water Heater

If your water heater is over 10 years old, there's a good chance that it has reached the end of its life and it will need to be replaced. However, before you buy a new water heater, it's worth your effort to troubleshoot the problem. If your water heater is leaking, many times the issue is repairable. However, if the source of the leak is from the tank itself, you will need to replace the unit.

Before installing a Gas Water Heater

  • Check the label on your old water heater. It should list the annual energy usage and the tank size. Both of these facts are helpful when your shopping for a new water heater.
  • We recommend inspecting your water heater vent system to ensure that it's in good repair and working properly before removing your old heater.
  • Disconnect and drain your old heater, then remove it with a hand truck. If your water heater tank has an excessive amount of sediment build-up, the drain valve may clog. This article will help you drain the tank.
  • Handle the vent pipe with care. If it's in good condition, you can use it with your new water heater. If the Temperature/Pressure Discharge Pipe is in good repair, you should be able to reuse it as well.
  • If your water heater was plumbed with copper pipes, you may need to cut the copper pipes with a tubing cutter. If so, be sure to leave as much pipe as possible.
Gas Water Heater in Garage

How to Install a Gas Water Heater

Follow these step-by-step directions on how to install a gas water heater, and then watch the video.

Install Earthquake Straps

Step 1 

Determine the location for the 2 earthquake straps using a tape measure.

  • These seismic straps will brace the tank against the wall during an earthquake and help prevent it from toppling over.
  • Measure from the ground up on the water heater and mark the wall appropriately: The top earthquake strap should be a few inches below the T&P Valve. The lower strap should be a few inches above the gas regulator.

Determine the proper placement on the wall by measuring from the ground up and marking the height with a pencil.

Measuring for Earthquake Straps for a Gas Water Heater Installation

Mount the earthquake strap bracket onto the wall. Be sure the screw "catches" a stud. The earthquake strap should rest next to the tank. If necessary, "swing" the bracket 180° before fully tightening the screws.

Move the new water heater into place. Set the water heater into a drain pan and line-up the existing plumbing to the water heater's inlet and outles connectors. Be sure to leave room between the wall an the ater heater to perform future maintenance.

Do Not strap the water heater into the earthquake straps.

Mounting earthquake straps when installing a gas water heater

Connect the Water Supply

Step 2

Clean the cold and hot water line threads with a wire brush.

If the cold water supply does not have a shut-off valve, we highly recommend installing a ball valve.

Preparing the pipes to install a gas water heater

Connect the hot and cold water supply lines.

If you're using copper flexible water lines (as shown in the video), be careful to avoid kinking them when installing. Loop the flex connector around using the technique shown in the video. Keep the hot and cold water supply lines clear of the vent area, and be sure to leave a little slack in both.

Some areas require the use of dielectric nipples between the water heater and the water line. Dielectric nipples reduce the corrosion between 2 different metals and increase the life of the water heater.

Check your new water heater before purchasing dielectric nipples. Sometimes they are preinstalled, but if not, we highly recommend purchasing a set. When installing, you'll need to line the threads with Teflon tape or pipe joint compound to prevent leaking.

Connect the water lines on a gas water heater installation

Install the Vent Hood

Step 3

Attach the vent hood over the flue on the top of the water heater. Be sure the follow the instructions that came with your water heater as the process varies from manufacturer to manufacturer. 

Use self-tapping sheet metal screws to secure the vent hood in place.

Installing the hood on a gas water heater installation

Install the Vent Piping

Step 4

If your vent pipe is in good condition, you should be able to reuse it with your new water heater. Check your water heater's manual for the correct vent pipe diameter. A reducer should NOT be used if the recommended vent pipe diameter is larger than the vent hood.

Installing the vent piping

Insert one end of the adjustable vent pipe into the water heater vent hood and begin attaching the other pipe sections. Be sure to check your water heater manufacturer manual for the correct diameter. 

Adjust the elbows on the Amerivent vent prior to installing. This will allow the vent pipe to align as closely to straight as possible. 

Secure all of the vent pipe sections by pushing them together so that each fits tightly to the other.

Installing the vent joints on a gas water heater

Use self-tapping sheet metal screws to secure the vent sections to the water heater vent hood and the other vent sections. Use at least 2 screws at each connection. Check your local code for requirements.

Securing vents when installing a gas water heater

Install the Gas Connection

Step 5

Double check that the gas supply is in the OFF position. Then use a wire brush and clean the pipe fitting on the supply pipe.

Flush the line by opening and closing the valve.

Prep the gas supply prior to connecting when installing a gas water heater

Remove the sticker and plug on the water heater's gas control valve. This is where the gas line will connect. 

Unscrew the gas nipple on the flexible gas line. Flexible gas lines are required in many areas, especially areas prone to earthquakes. It's always a good idea to check if they are allowed in your area. 

Preparing the gas control valve when installing a gas water heater

Paint pipe joint compound onto the thread of the gas nipple. Avoid covering the first few threads with pipe joint compound as shown in the video. Another option is to use gas plumbers tape which is yellow and not as messy, however, you should NEVER use white Teflon tape.

Preparing the gas line when installing a gas water heater

Insert the gas nipple into the gas control valve and tighten the gas nipple with a wrench. It should be fairly tight. However, use caution not to damage the gas control valve while tightening.

We recommend tightening the nipple with 2 wrenchs to prevent damage. One wrench on the nipple, and the other holding the gas control valve.

Installing the connector to the gas control valve when installing a gas water heater

Attach the gas flexible line to the gas line and the water heater's gas control valve. Be careful not to kink the line. Loop the excess line if necessary.

Hand tighten the connectors and then, use a wrench to tighten slightly tighter. Do NOT turn on the gas.

Attach the gas line when installing your gas water heater

Fill the Tank

Step 6

Open the water inlet valve and begin filling the tank with water. Open a hot water faucet, this will alert you that the tank is full.

Check for leaks on each end of the hot and cold flexible water lines while the tank is filling.

When water runs from the hot water faucet, the tank is full. Allow the water to run for several minutes. This will eliminate the air within the tank. The water will sputter until the tank is full and all the air has been bled fromthe tank and lines.

Fill the Tank during a gas water heater installation

Connect the Earthquake Straps

Step 7

Pull the earthquake straps around the water heater and connect them together. Do not pull the straps too tight, they should be snug, but not too tight. Then use clips to fasten the excess strap.

Secure the earthquake straps when installing your gas water heater

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Connect the T&P Drain Pipe

Step 8

If your T&P drain pipe is in good shape, you may reuse it from your old water heater. 

However, you may need to make a new T&P drain pipe. To do this, measure and cut a copper pipe with a tube cutter. If you do not have a floor drain, place a bucket under the T&P drain pipe. The end of the drain pipe should be no higher than 6-inches above the ground or bucket.

Installing the T&P drain pipe when installing a gas water heater

Light the Pilot

Step 9

Turn the gas supply ON.

Follow your water heater's owners manual to light the pilot. The procedure can vary between manufacturers.

Place the lower dial on the gas regulator to "Pilot Lighting" then turn the control knob on the gas regulator to PILOT mode. Press and hold down the control knob. Wait a few seconds, and then press the ignitor button, while you are pressing the control knob.

Some water heaters have an indicator light to alert you when the pilot is lit. Others have a sight glass that will allow you to visually check if the flame caught. 

If the flame went out: Repeat the above steps.

If the flame caught:

  • Continue pressing the control knob for 45 to 60 seconds.
  • Release the control knob and check that the pilot is still lit.
  • If the pilot is still lit, turn the control knob to the ON position.

Turn the lower dial to your desired water temperature. Use the factory recommendaion setting as your starting point. 120° is the recommended temperature setting. 

Lighting the Pilot when installing a Gas Water Heater

Test Gas Lines for Leaks

Step 10

Check for gas leaks by spraying all gas connections. You can mix your own solution (1 part dish detergent and 2 parts water), or, use Leak Detection Solution.

If you notice any "bubbling" it's an indication that gas is escaping. Tighten the loose connection with a wrench and then check again.

Check for gas leaks when installing your gas water heater

Watch the Video

Other Considerations

Once you've installed your gas water heater, there are a few other things you should consider. First, always check your vents to make sure they are properly drawing. If they are not, we recommend contacting a professional to help you resolve the situation. The video below will show you how.

Watch the Video

After a couple of hours, check the T&P discharge pipe. If the pipe is dripping, there is a good chance that the pressure inside your tank is too high. Turn off the gas supply and call a professional immediately.

We highly recommend having a carbon monixide detector near your gas water heater. They are inexpensive and will alert you to a dangerous situation.

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