When your water line is shut off, cold water stops flowing into your home entirely, and if your water heater has a tank, the tank will stop refilling with cold water. If your water is shut off for long periods of time and you use your hot water heavily, this can create the risk of serious damage.

You should turn off your water heater if the water is off only if your water is turned off for an extended period of time, like a vacation, and you have a tank-type or hybrid water heater. For short term shutoffs, you can leave your water heater on until the cold water starts flowing in again.

This article will discuss the kinds of water heaters, how they connect to a water line, and what to do if you need to shut your water off or experience a shutoff for any reason.

How Water Heaters Work

The water that enters your home through a water line and the connected pipes is usually cold or cool, even in the summertime. For you to have warm water in the home, the water needs to be heated after it’s delivered through the pipes.

Water heaters are usually found in a home’s basement and require a gas or electric heating unit. There are four basic types, each of which performs this same function in different ways. The four basic types are:

Tank-Type Heaters

Tank-type heaters are the most popular kind of water heater. Basically, it consists of an insulated tank filled with water, above or beside a gas or electric heating mechanism. The cold water enters the bottom of the tank, then rises as a gas flame or electric element heats up the water. A pressure-relief valve keeps the heater from becoming too pressurized.

When an appliance or faucet needs warm water, the water tank pumps hot water out through the top of the tank, then replaces it with new, cold water at the bottom. Though this process repeats continually, these heaters can sometimes struggle to keep up with high demands for hot water.

Tank-type heaters also use energy continuously to keep the water in the tank warm even when it is not needed, which makes them less efficient than some alternatives.

Tankless Water Heaters

Tankless water heaters are much smaller than the tank-type heaters because they do not store water. Instead, the heater waits for a hot-water tap or appliance to demand warm water, then initiates an electric element or gas burner and draws cold water directly over the heating mechanism and to where it is needed.

Tankless water heaters last much longer than tank-type heaters and produce an unlimited supply of hot water, but are much more expensive to purchase, install, and repair.

Hybrid Water Heaters

Hybrid water heaters use less energy than a tank-type heater, but more than a tankless water heater. Essentially, the hybrid works by storing water in a tank connected to an air compressor, which captures heat from the surrounding air and transfers it to the cold water, instead of using a gas flame or electrical elements.

Point-of-Use Heaters

Point-of-use heaters are small and compact and are usually used in combination with the main water heater. Generally, point-of-use heaters are installed at fixtures far away from the main heater to avoid running the water and waiting for the water to become warm. These electrically powered units heat the water instantaneously, eliminating wait time.

Point-of-use heaters typically last a long time and can be installed very quickly and easily, but cannot replace a main water heater in the home.

How the Home Water Line Works

If your home is connected to a city water line, then your water main can be identified by locating a ½” to 1½ ” pipeline near your water meter. You may or may not also see an emergency shutoff valve, which would cut off all water headed into your plumbing system. If your home is connected to a water well, your system may look slightly different, but the function is the same.

The water that enters your home through the main water line is pressurized, which allows it to travel against gravity through your pipes. This means that water can flow very quickly, whether from a faucet, hose or through a broken pipe in the case of an accident. If you do have a broken pipe, it’s important to use your emergency shutoff valve to avoid heavy flooding.

Water leaves the house through separate drainage systems, which use gravity to pull water down, creating a flow that carries wastewater through pipes and to a sewage treatment facility or septic tank.

The Water Line and the Water Heater

Water that enters your house is cold and travels through cold water pipes. One of these pipes connects to the water heater. Your water heater also connects to a hot water line, where water flows out to different appliances and taps. Water flows into and out of the heater as needed.

What Happens to the Water Heater When Your Water Is Turned Off?

When your water is turned off, cold water stops flowing into your plumbing system from the outside, meaning that a tank-type or hybrid heater stops being able to refill with more water. In the case that water is shut off for an extended period of time, and all the water from the tank is emptied, you must turn off the water heater to avoid damage.

However, if your water heater is full or nearly full, you shouldn’t need to turn it off in a short-term water shutoff.

Tankless and point-of-use water heaters do not need to be shut off in any case to a water shutoff, as they do not run heating elements continuously or hold water in a storage tank.

When to Turn Off Your Water Heater

Turning off your water heater may be necessary in the case of a plumbing emergency, like in the case that your cold water line loses pressure and fails to fill the water tank, or in the case that your water tank empties for any other reason.

In other cases, turning off your water heater may be desirable, but not necessary, like in the case of a leak. Leaks can happen for a number of different reasons:

  • Loose valves
  • Damaged tank
  • High pressure
  • High temperature
  • Improper drainage
  • Old age

If you’re simply looking to save money by avoiding running the water heater when it’s not being used, it’s best to turn the temperature down instead of completely turning the unit off. Water heaters can be difficult to turn back on, and you may find yourself without hot water for longer than you’d like.

If you decide to turn off your water heater, make sure that you work carefully and understand your water heater’s components before making any adjustments. A water heater’s components are:

  • The shutoff valve stops the flow of cold water into the water heater and is typically located outside and above the unit.
  • The drain valve is usually located near the bottom of the tan and empties water and sediment from the storage tank.
  • The pressure relief valve keeps the pressure inside the tank within safe limits.
  • The heating mechanism may be gas or electric and is the most important part of the tank to shut off if you are concerned about an empty tank following a water shutoff.

To turn off your water heater, following the following instructions in this video:


You do not need to shut off your water heater if the water is off in most cases. However, in the unlikely case that you’ve had your water shut off for an extended period of time and used all the water in your water heater tank, then it is necessary to turn off the water heater. When in doubt, call a professional plumber.

Write A Comment