How Gas Tank Water Heaters Work

Gas tank water heaters are some of the most common water heater types. They are less expensive than their tankless water heater counterpart, which contributes to their prevailing popularity. While the technology is simple, it is good to know how a gas tank water heater works, whether to satisfy your curiosity or make an informed decision about your next water heater purchase.

The Basics

We all know the function of a water heater is to heat cold water, and gas tank water heaters store that hot water (and keeps it hot) until you need it. You may also know that heat rises. The cold water supply line (also called the dip tube) introduces cold water by directing it to the bottom of the tank. The cold-water supply tube forces water to the bottom where a gas burner below the tank will heat that water. As the water warms, it will rise, and hot water is drawn from the top of the tank and into the plumbing. The hot water discharge pipe only needs to draw hot water from the top so the pipe can be much shorter than the cold-water supply tube. The inside of the tank has a plastic or glass layer bonded to the steel to prevent rusting on the interior.

Gas Water Heaters

How hot you keep the gas tank water heaters depends on the gas controls. A gas regulator assembly will be somewhere on the side of the water heater. You can control the temperature from there and turn the burner off and on. It is important to know where the gas shutoff valve is so you can turn off gas to the heater when you need to. The pilot light will always be on and lights the burner when the system calls for it. The gas flows from the gas regulator and into the gas burner assembly at the bottom of your water heater. You can access this area through a panel for needed repairs or replacing a thermocouple.

Exhaust Flue

An exhaust flue allows gases to exit the house through a vent or chimney. The flue is a hollow cylinder in the middle of the tank. Not only does it exhaust gases, but it also helps heat the water in the tank. The heat from the exhaust gases is captured and transmitted to the water tank.


Like most other plumbing fixtures, gas tank water heaters come with their share of valves that are handy to know how and when to use them. The temperature and pressure relief valves relieve excessive temperature and pressure that has built up in the tank. It’s usually located at the top of the tank, and if you open it, water should come out of the overflow pipe. The tank drain valve, on the other hand, is located near the bottom of the tank. You can drain sediment out of your tank through this valve.

If you need repairs on your gas tank water heaters or if you are in the market for a replacement give Valley Fire Protection & Plumbing a call. We have knowledgeable plumbers on staff that can help you with your water heater repairs.

Related Topics: Plumbing // Water Heater
By: Tom Hartel
I acquired my expertise by directing day-to-day operations of the business for over 20 years. Continuous hard work helped me become a nationally recognized speaker and expert on fire protection, fire sprinklers, special hazards, and plumbing systems. In this blog, I share my knowledge that will hopefully help you make better decisions for your projects.


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