How to Install a Gas Water Heater in 7 Simple Steps

Josh Miller

Josh is a contributing writer to the site and former HVAC specialist.

Last Updated on January 19, 2022

Most conventional water heaters last about 8 years when well-maintained. After that time, you’ll have to replace your old tank with a new one.

Installing a new gas water heater isn’t complicated, but it’s helpful to have some experience working with pipes. Whenever you need to install gas pipes, it’s better to ask for the help of a professional if you don’t feel completely comfortable.

Installing a gas water heater involves a series of simple steps. You need to drain the old water heater and disconnect the old pipes. Consider if you want to install a thermal expansion tank, which increases the efficiency of your water heater. 

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Table of Contents

Conventional Or Tankless Gas Water Heaters

When installing a new water heater, it’s a good idea to consider if you want to switch to a different model type. Tankless water heaters offer the benefit of having hot water on demand, and they can be helpful for large families.

The installation is slightly different depending on whether you are using a conventional or tankless water heater. A tankless water heater installation tends to be more complicated, and you might need the help of a professional.

Tankless water heaters can be 100% electric or run with a combination of gas and electricity. In any case, you’ll need to work with both pipes and wires, which might be a bit of a challenge.

water tank controls

Before Installing a New Tank

Before installing a new tank, check your home’s water pressure using a pressure gauge. You can connect the gauge to an outside water spigot. As long as the pressure is between 50-60 PSI, there’s nothing to worry about.

If the pressure is lower, consider installing a pressure booster pump. This pump increases the water flow in your home. If you have a pressure higher than 80 PSI, you should install a pressure reducing valve for safety reasons.

Also, consider installing a thermal expansion tank to protect your water heater. Usually, this tank connects to the cold water supply pipe. Water expands when heated, and this tank absorbs some of that extra pressure.

How to Install a Gas Water Heater in Simple Steps

When learning how to install a gas water heater, make sure you are comfortable cutting and soldering copper pipes. Whenever gas pipes are involved, it’s always safe to ask for the help of a professional plumber. If you decide to do the installation on your own, use appropriate tools and parts.


Step 1: Check the Vent

The first thing you should do is check the state of your old vent. You can easily do this by lighting a match and putting it close to the vent opening right on top of the water heater. If the vent quickly sucks the smoke, it’s working correctly. If the smoke blows back, you have a venting problem. Ask for the help of a specialist to see how you can solve it.

Step 2: Drain Your Old Water Heater

Before installing your new tank, you have to move the old one out. And to do this, you need to empty all the water. Start by closing the gas valve. Open a hot water faucet and let it run until there’s no hot water inside the tank.

Connect a hose to the drainage valve on the tank’s bottom to drain it. Take the other end of the hose out into the garden or use a pair of buckets. Open the drainage valve, and the water should start flowing out. You might need to open a faucet or open the pressure relief valve. This brings some air inside the tank and helps empty it.

Step 3: Disconnect the Tank

Once the tank is empty, you can disconnect the gas pipe, water pipes, the vent system, and the pressure relief pipe. If the pressure relief pipe is a straight pipe leading to a bucket, you can use the same pipe on the new water heater for the same valve. When cutting the water pipes, leave them as long as possible.

Step 4: Place the New Tank

When learning how to install a gas water heater, there are small things you can do to improve your experience with your new tank. For example, consider placing the tank on a drain pan. You can connect the drain pan with a pipe to a nearby drain.

Also, if you live in an area with hard water, consider installing an anode rod inside the tank. An anode rod attracts harmful minerals and prevents the tank from taking all the damage. You should change the rod every 3-5 years.

One of the main reasons why water heaters malfunction is due to the minerals in water accumulating inside the tank and cause corrosion. Eventually, they can damage the heating element and break through the tank’s inner lining, flooding your basement or apartment.

Step 5: Connect the Water and Gas Pipes

Install the discharge pipe on the pressure relief valve. If you don’t want to connect the pipe with a nearby drain, you can simply place a bucket underneath it. The next step is to connect the water pipes and gas pipes. Use copper pipes or flexible steel hoses.

Step 6: Check for Water Leaks and Fill the Tank

You should check for leaks on the water pipes and the gas pipe leading to the tank. Keep the gas turned off and open the cold water supply valve. Check the cold water connection for leaks. Open a hot water faucet and wait until the water runs from the tap. When water comes out, the tank is full. Check the hot water pipes for leaks as well, but be careful.

Step 7: Secure the Venting and Connect the Gas Pipe

Secure the new exhaust hood on the tank. This should be pretty straightforward. To connect the gas line, make sure the tank’s control knob is off.

After connecting the line, turn the gas on, and check for gas leaks using a leak detector solution. You can also use a mixture of dishwashing soap and water. Apply any of the two liquids on the line’s connections. If bubbles appear on the surface, there’s a leak. Try tightening the connections a bit more and do the test again.

Flush and Drain the Tank to Increase its Longevity

Now that you know how to drain a tank, you can apply the same process to drain and flush your tank once a year for maintenance. You need to clean the tank’s inside at least once a year to avoid corrosion and increase its lifespan.  

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