One of the most nagging questions first-time water heater owners ask is, “should I turn off water heater if water is off?” And although some plumbers say you should, other people counter that everything depends on the situation.
The varying opinions deserve a closer look. Continue reading to learn more about whether shutting off water to water heater units requires cutting off the power to the appliance.
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Should I Turn Off My Water Heater If There’s No Water?
The short answer to this is, yes, you must turn off water heater if no water is in the storage tank.
Water heaters, especially electric models, are susceptible to dry-firing because the heating elements are not in their correct environment (submerged in water).
Experts say water removes 23 times more heat than air (higher thermal conductivity).
So, when you submerge the heating elements in water (such as during normal water heater operation), you rely on water’s thermal conductivity to raise liquid temperature without causing the heating elements to turn too hot.
Meanwhile, emptying the tank while leaving the water heater running exposes the heating elements to air. Because air does not remove heat as efficiently as water, the heating elements will become very hot.
Hence, it is always a sound decision to turn off the water heater when there is a water outage in your area.
For example, the local utility might conduct repairs or maintenance of city plumbing systems, requiring them to shut off the water supply during the activity. Your heating unit might not receive water for several hours.
In some cases, construction work might also disrupt the water supply, leaving many homes water-less. Natural disasters can damage public utilities, including pipelines.
Of course, water supply disruptions are not the only instances you might want to turn off the water heater.
Under What Circumstances Should I Turn Off the Water Heater?
1. Leaving home for several days
An example of an instance where you can turn off the water heater is when you go on an extended vacation or leave home for several days.
Experts say electric water heaters should not be powered on if there is no liquid in the tank for over 24 hours.
However, it is worth pointing out that many modern water heaters have a “vacation” mode, allowing homeowners to activate the feature when they go out for several days.
You do not need to power off the water heater if it has this VAC mode.
2. Water heater storage tank leaks
Leaks in the water heater also require turning off the appliance. Most water heaters leak because of a failing temperature-pressure relief (TPR) valve. Too much pressure can cause the tank to burst or explode.
Turning off the water heater in a TPR valve failure allows plumbers to address the problem safely.
3. Power outages
A power surge is a threat to all electric appliances during power outage events. Cutting off electricity before restarting can deliver between five to thousands of volts to devices, including water heaters.
Unsurprisingly, authorities recommend turning off all electronic devices and appliances in a power outage.
The Importance of Turning Off Water Heater If Water is Off
It is easy to imagine what will happen to your water heater if you leave the water heater turned on without water in it.
Consider boiling a pot of liquid on a stovetop, and you let it simmer until all the water evaporates. What happens? The pot will be smoking hot, with its bottom charred beyond recognition.
It is the same thing with water heaters, especially electric versions.
Electric water heaters have metal heating elements that require complete water immersion during operation.
These heating elements can become super-hot and dry-fire if water turned off, leaving only air around them.
Dry-firing shorts the heating elements, rendering them useless. The water heater might even explode because of excessive heat and pressure within a contained space.
You might want to watch Mythbusters’ video if you do not believe it.
MythBusters – Exploding Water Heater
Would a water heater explode if turned off? It won’t.
How Does a Water Heater Work?
As the name implies, a water heater works by raising the temperature of the water passing through a heat exchanger (for tankless systems) or stored in a tank (tank-type water heaters).
Regardless of type, cold water enters the appliance and comes out hot.
Gas-powered water heaters have a burner at the storage tank’s bottom, like a stove top heating a pot of water. Meanwhile, an electric water heater has heating elements (like heating rods in an oven) that raise the temperature.
It is a similar mechanism for tankless water heaters, except the cold water snakes through an extensive network of heat exchanger coils. These tubes are super hot, allowing them to raise the water’s temperature.
Hence, the water heater cannot serve its function if cold liquid does not enter the storage tank or run through the heat exchanger coils (i.e., no water supply).
Tips to Turn Off Water Heater
You now know it is advisable to turn off water heater when water is off. But how do you turn it off? Are there any tips you should consider? We recommend the following.
- Although your water heater might have a dedicated ON/OFF switch, it is still safer to disconnect it from its principal power source.
In this case, turn off the water heater’s circuit breaker at the electrical panel.
To turn off gas water heater if water is off, you might want to close the gas shutoff valve, rotate the temperature dial to the OFF position, and ensure the pilot light is unlit.
- Homeowners must close the central water shutoff valve by twisting the handle or knob into the OFF position.
- Draining the storage tank is also a good idea, especially if you leave the house for several weeks. You can connect a hose to the tank’s drain port, open it, and empty the water. Opening a hot water faucet can quicken the draining process.
- Storage tank water heaters have temperature-pressure relief valves. Locate these parts and turn them to the OFF position.
Frequently Asked Questions
Does turning off the water heater save money?
It depends. You can save up to five percent if you turn off the water heater only occasionally and over extended periods (at least two weeks).
For example, suppose you pay $50 for your monthly electricity. You can save $2.50 on your next electric bill if you switch off the water heater for at least two weeks.
Meanwhile, turning off the water heater for several hours every day might be costlier because the appliance will use more energy to heat the now-cold water in the tank.
Moreover, you risk damaging the water heater because of frequent on-off.
Can I turn off the water supply without shutting down the water heater?
Yes, you can switch off the central water shutoff valve without turning off the water heater.
However, this activity is only safe if the water heater storage tank is full or its heating elements are submerged in water. A half-empty tank exposes the upper heating element. Because the water heater is on, the exposed heating element can become too hot and increase in-tank pressure.
You will also want to turn off the water shutoff valve AND the water heater if the main water supply line loses pressure.
We offered several points to help you answer the question, “should I turn off water heater if water is off?”
Leaving home for at least two weeks or not using the water heater over extended periods is one of the most common instances requiring turning off the water heater.
Leaks in the device’s storage tank and defects in the TPR valve also require turning off the water heating appliance. You will also feel safer when power resumes after a blackout by switching off your electronics.
As the founder of Usawaterquality, I have been working to deliver quality advice on utilizing water components for numerous households. Here, we believe that water quality is the most critical part of health care, so the investment and attention for the water system will never go to waste.