How Does Your Gas Water Heater Work? An In-Depth Guide

Published On: November 18, 20192 Comments on How Does Your Gas Water Heater Work? An In-Depth GuideTags: Last Updated: February 12, 20245.4 min read

If you live in a home and enjoy the luxury of a hot shower, you can thank a water heater. If you’re the homeowner, you should get to know how your gas water heater work. A little knowledge goes a long way. It’s especially helpful on the day you want to take a hot bath and all that comes out of the spigot is ice cold water. Read our guide about gas water heaters and how they work.

How your gas water heater works

The information may help you troubleshoot your water heater, but it’s also great material for dinnertime conversations.

The Insides of a Gas Water Heater

Don’t fear what you don’t know about the appliance toiling away in your basement or utility closet. We know they sometimes make strange noises and are the topic of some pretty wild stories. But in reality, your water heater isn’t that complicated—here’s an inside look.

All conventional gas water heaters have similar components including:

  • Tank
  • Dip Tube
  • Discharge Pipe
  • Gas Burner and Assembly
  • Pressure Relief Valve
  • Drain Valve
  • Exhaust Flue

If you have a tankless gas water heater, your system uses different components including:

  • Heat exchanger
  • Gas valve
  • Burner
  • Ignition system
  • Combustion chamber
  • Combustion fan
  • Temperature sensors
  • Vent
  • Water valve

For households that only average of 41 gallons of hot water use per day, a tankless system is a viable option. We’ll keep the focus for this post on tank water heaters since that’s what more homeowners use right now. Next, we’ll take a quick dive into your water heater components.

The Water Heater Holding Tank

You’ll notice the biggest piece of your water heater is the tank. The tank holds anywhere from 30-80 gallons. (If you have an 80-gallon tank, you have a huge family. Water enters the tank through the dip tube. Of course, this isn’t hot water, it’s cold water from the main water supply line. The dip tube runs from the top of the tank to the bottom. The water heats up inside the tank, then rises to the top, exiting through the discharge pipe. Also called a drain line, the discharge pipe routes the water to fixtures like your sinks, shower, dishwasher, and washing machine.

Tip: Find where the cold water line enters the tank and locate the shut-off valve. You’ll want to know where it is in case you have an emergency.

The Heat Source

You’re probably wondering how gas water heater work and how the water heats up inside the tank, right? Since this is a gas water heater, your heat source is a gas burner. The gas burner sits under the tank. You control how hot it gets your water with a control module, also called a thermostat. Most manufacturers place the control module on the side (toward the bottom) of the tank where you can reach it. If you have an older water heater it may ignite with a pilot light. If so, you’ll also use the control module to light the pilot light should it go out. Newer water heaters often use pilotless ignition.

Tip:  There’s a gas line located on the side of the tank with a shut-off valve. Use it if you need to turn off your gas supply.

Is a Natural Gas Water Heater Safe?

We mentioned noises earlier (and wild stories). You can relax because all water heaters make a bit of noise—we’ll talk about the worrisome noises in a minute. As for the wild stories, you’ve heard tales of water heaters starting fires and shooting through roofs. Those are rare occurrences and typically happen when people either leave flammable materials too close to the water heater or fail to take care of routine maintenance. Natural gas water heaters have several safety mechanisms designed to prevent things like fires, explosions, and gas leaks. We’ll show you two of the most critical.

gas water heater parts

The Exhaust Flue

As anyone else who provides heating services can tell you, when you use natural gas as a fuel source, you have combustion. Combustion generates gasses like carbon dioxide, carbon monoxide, and nitrogen oxide. The exhaust flue vents these gasses outside of your home preventing you from breathing them.

Temperature & Pressure Relief Valve 

Another safety mechanism found on gas water heaters is a T&P valve. If either pressure or heat builds up too much in the tank, this valve goes into action. It’s located at the top of the tank and you’ll feel relieved to know it prevents the tank from exploding. If you’re wondering where the water goes if the T&P valve triggers, the valve has an overflow pipe attached to it that drains the water away from the water heater.

Tip:  Use caution if you’re replacing an overflow pipe. Some are made from PVC and if your water discharges steam or extremely hot water, PVC pipe can melt.

What About Noise?

We’re pretty sure one reason people avoid contact with their water heater is fear. When you have an appliance sitting in a dark basement, attached to your natural gas line, and it makes noise, it’s not exactly approachable. For many homeowners, it’s the weird noises they hear that keep them away. Here are a few common sounds made by gas water heaters and a reason for each one.


When a water heater makes popping sounds, it usually means there’s a buildup of minerals and sediment at the bottom of the tank. Prevent popping by having your plumbing technician do a flush-and-fill each year.


Don’t worry about crackling sounds. It’s likely condensation on the burner.


When leaking water drips on the burner, it sizzles. If the sizzling is accompanied by no hot water, you probably have a leak. Call your plumber!

Now You Know Your Gas Water Heater

There’s much more you can discover about your gas water heater but for now, you should have enough to gain a better understanding of one of your home’s essential appliances.

If you’ve enjoyed reading this post about how gas water heater work, then we hope you’ll spend more time on the blog. You’ll find plenty to browse through if you like DIY and home improvement. Thanks for reading!

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Leave A Comment

  1. Anonymous March 18, 2021 at 12:40 am

    It would be helpful if this had a few photos of the mixer valve which controls the water temperature. Otherwise a well written guide. Thanks

  2. Alex Daniel January 25, 2020 at 1:22 am

    Very helpful guide guys !!

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