How to Turn on a Water Heater

Co-authored by Dave Jones

Last Updated: August 12, 2024 Fact Checked

Whether you have an electric water heater or a gas water heater, you can turn it on without having to call a professional to help you. An electric water heater requires finding the circuit breaker and turning it on, while a gas water heater needs the pilot light to be lit. One of the most important steps is making sure your water heater is entirely full of water before starting it up.

Method 1

Method 1 of 4:

Making Sure the Water Tank is Full

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1
Shut off the water supply and gas valve or circuit breaker. Turn the gas valve to "Off," or make sure the breaker switch for the water heater is off at the circuit breaker. To turn the water supply off, twist the valve for the cold water supply line that enters the tank (usually from above).
- The breaker switch for your water heater should be labeled, but if it isn't, go ahead and turn off the main power.^{[1]
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2
Drain and flush the tank to clean it out. To drain your water tank, attach a hose to the bottom of the tank where the spigot is. Choose a hose that's long enough to stretch to a nearby floor drain or utility sink, or all the way outside to the yard. Then open the drain valve on the water tank to start the draining process. By opening a hot water tap close to the tank, you'll help it drain faster while also being able to check on its progress. Open the cold water supply valve again to flush out any extra residue or minerals from the tank.
- Let the cold water flush through the drain valve for 5-10 minutes.
- You can skip the flush if it's a newly-installed tank. Don't attach the hose or open the drain valve, and use the nearby hot water tap to know when the tank is full -- a steady stream of water without sputtering is the sign.
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Once your tank has been flushed out and clean water is coming out of the hose, close the drain valve and take off the hose. Your water tank should now begin to fill back up. Keep the tap open on the nearby faucet so that air can escape while the tank fills up.
Your hot water tap is how you'll know when your tank has filled up.^{[2]
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Research source} Once you see and hear a nice, steady stream of water come through the faucet, your water heater is full. If you hear sputtering, this means air is still being forced out of the tank. You can close the tap once it has a steady stream.
Now that the tank is full, you're ready to turn on the water heater. If you're dealing with gas, switch the gas valve to the "On" position when you're ready to ignite the pilot light. For electric water heaters, turn the circuit breaker back on.

Method 2

Method 2 of 4:

Starting a Modern Gas Water Heater

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1
Set the temperature and On/Off controls to the right setting. Before starting the water heater, turn the temperature control to the lowest setting. The On/Off control will need to be switched to the "Pilot" setting.
- If you smell gas or a rotten egg odor, don't go any further until calling your gas company — you could have a gas leak.
While you're holding down the pilot igniter button, press the spark generator. This should create a spark that you can see through the little glass window, showing you that the pilot light is lit.
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Keep pressing the pilot igniter button for 20-30 seconds. After you see the spark, don't let go of the pilot igniter button yet. Keep pressing it for 20-30 seconds so that it's able to get hot enough before being released.
- You may have to press the spark generator down every 10 seconds until it properly lights if it isn't lit after 30 seconds.
4
Turn the control to On and the temperature to the desired setting. Switch the On/Off control to "On." Then turn the temperature setting to your desired temperature. Most people set theirs to 120 °F (49 °C). At this point, you should be able to see flames through the small glass window.
- It is not recommended to set the thermostat above 120 °F (49 °C) due to the risk of scalding.

Method 3

Method 3 of 4:

Igniting an Older Gas Water Heater

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1
Turn the temperature down and the On/Off control to the "Pilot" setting. Before turning the gas on, turn the temperature to the lowest setting. Switch the regulator valve to “Off” and wait 10 minutes. After the 10 minutes have passed, you can switch the valve to “Pilot."
- Call your gas company if you smell a rotten eggs odor. This could be a sign that you have a gas leak.
Your water heater may have inner and outer access panels that need to be removed. If this is the case, take out the access panels in order to get to the pilot light. The access panels usually just slide right out.
Keep the pilot button pressed down so that you'll be able to start up the water heater. If your model doesn't have a specific pilot button, press and hold the On/Off control.
Find the small silver tube that is connected to the gas control valve — this is the pilot supply tube. Follow the silver tube to the end and use a long neck lighter to light the pilot.
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Keep the pilot button pressed for 20-30 seconds before releasing it. Once you've lit the pilot, continue to press down on the button for 20-30 seconds. After the time has elapsed, you can slowly release it and the pilot should continue to stay lit.
- If your pilot light goes out, light the pilot again and hold the pilot button down longer than the previous time.
If your water heater has access panels, it's time to put them back in place. Forgetting to do this could cause serious injury if the flames suddenly flow out of the opening due to gas build-up.
Switch the On/Off control to the "On" position, and put the temperature control to the setting you wish — 120 °F (49 °C) is recommended. After you've set the controls, you should hear your water heater firing up.

Method 4

Method 4 of 4:

Turning On Electric or Tankless Water Heaters

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1
Turn on the breaker for the hot water tank after it's full of water. For an electric water heater, you’ll need to locate the circuit breaker that controls the heater and turn it on. If the breaker isn’t labeled, look for a double-pole breaker that has the same amp rating as the heater. Simply switch on the breaker to turn on the electric water heater.
- The amp rating should be labeled on the water tank.
It will take your water heater several hours to completely heat up, so check it periodically by turning on a faucet to make sure it’s getting warm. The recommended temperature is 120 °F (49 °C).
It's important to make sure the gas is turned off before starting up your tankless water heater. Tankless water heaters will need to be turned on by flipping the corresponding breaker, or by flipping on a switch.
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Confirm the temperature and turn on the gas for the tankless water heater. Once you've turned on the power, you can adjust the temperature using the temperature controller, which is often digital. Turn the gas supply on, and that's it!
- Tankless water heaters operate on-demand, so it will only start heating water once you need to use it.
- Since these water heaters are tankless, you don't need to fill them up with water.

Community Q&A

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Question

How do you light an electric water heater?

Drew Hawkins1

Community Answer

Electric water heater do not need to be lit. Locate the circuit breaker that controls the heater and turn it on. Wait a few hours so the water tank can heat up. Turn on a faucet periodically to make sure it's getting warm. When the water reaches 120 °F (49 °C), then the tank has fully heated.

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Question

How do I reset my hot water heater?

Drew Hawkins1

Community Answer

Look for a red button on the side of the water heater that says "Reset." Some water heaters have a reset button that is hidden beneath the thermostat. When you locate it, press the button firmly. It may make a clicking sound when it resets.

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Question

How long do you have to wait for hot water to come back?

Drew Hawkins1

Community Answer

Gas water heaters can heat up a tank of hot water in about 30 minutes. Electric water heaters can take a couple of hours to heat the water in its tank. Once the water tank has been heated, you'll have hot water again.

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Warnings

If there are drips coming out of the discharge pipe, it may mean the pressure is too high. Turn it down so that it's below 80 psi.

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For a gas water heater, always check to make sure you don't smell a gas leak — or rotten eggs odor — before lighting the pilot light.

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