How To Turn On Water Heater? [Gas, Electric, Tankless Water Heaters – Complete Guide 2021]

Have you ever taken a bath when the tankless water heater was off? Was it enjoyable? Probably not.

Whether you have installed a new heater or moved into an apartment that has been empty for a long time, you need to know how to turn on water heater.

It may look like a technical piece of equipment, but you can turn it on without requiring professional help.

There are some differences between different types of devices such as electric, gas, hybrid, and solar, but there are some fundamental steps common to all of them.

In this guide, you will learn how to turn on each type of unit as well as how to turn them off and on every time you go on holiday and for cleaning purposes. So, let’s begin.


How To Turn On Tankless Water Heater?

These machines have a different starting procedure than other kinds of devices. As they are tankless, so you won’t have to wait for a long time to get hot water.

Once you turn them on, they start producing warm water instantly. Follow these steps to turn on your tankless appliance.

Turn On Breaker

It does not have a container, so there is no need to fill it with water like other water heating systems as long as it is attached to the water supply. Simply turn on the breaker. 

Check The Temperature

Now, it’s time for you to select a suitable temperature since the machine operates based on your demand.

It will heat up the water depending on the temp you select with the help of an adjustable thermostat present right above the unit.

Also, it will begin heating only when you turn on the faucet. The temperature of many heaters is set to 140 degrees Fahrenheit by default, but you can modify it easily whenever you want.

How To Turn On An Electric Water Heater?

They don’t have a pilot, so the procedure is quite simple. The steps to start an electric heater are as follows:

Turn Off Open Fixtures

If you are trying to start a hot water boiler, open a fixture to permit the air flow in the container. Your act should prevent the occurrence of an airlock. If you want to turn it on again, close the fixture by now.  

Turn On The Cold Water Supply

Don’t turn on the gas and light the pilot before refilling the boiler.

It is necessary to turn on the cold water to avert the turning back of the heating component to the container.

After that, the tank will fill up itself if it drops any water while working on the boiler.

Safety Tag

All electric units have a safety tag that you utilize while shutting off the unit. It prevents the accidental turning on of the heater while it is not in use.

So, carefully remove it before the power is turned on. Also, make sure that your hands are completely dry and it would be best if we wear gloves. Try to protect yourself from electric shocks.   

Turn On The Breaker

In most situations, electric devices don’t have an indicator light that informs that the appliance is on. Usually, the engine sound indicates that heating components are functioning and beginning to get heating.

After some time, the water will start heating and within one hour, you will get perfectly warm water. Keep checking your hot water fixtures to confirm the water is becoming hot.

Navien Tankless Water Heater Error Codes Troubleshooting

How To Turn On Gas Hot Water Heater?

To turn on a gas device, follow these steps.

Turn Off The Gas Valve

The first step of how to turn on hot water heater in apartment is to examine if any valves or fixtures have been opened, either accidentally or by you while you were cleaning your tank.

If it is open, a little bit of air will go into the tank. While turning on the device, make sure to close all the fixtures and valves.

Turn On The Cold Water

The next step of how to turn on the hot water heater is to turn on the cold water. You have to do this to allow the tank to fill up.

Lastly, you have to turn your machine on with a container that is not full.

Light The Pilot Light

It is critical to light your unit’s pilot light so that you can enjoy long showers.

Also, it is necessary to do it to prevent any accidents from the discharge of gas.

Turn On The Gas Valve

The last step of how to turn on water heater is to turn on the gas valve. If it is turned to “pilot”, then there is no need to follow the pilot light step.

You simply have to turn on the gas valve. At this time, your device should be warming up the water already and the burner should also be fired up.

However, if this is not the case, then you have to follow the pilot light step of how to light a water heater with electronic pilot.

How To Turn On Water Heater

How To Turn On Water Heater? Precautions To Follow

  • Check the discharge pipe for drops. If you witness any leaks or drops, there are possibilities that the pressure may be extremely high, turn it down immediately. It should be less than 80 psi.
  • While activating a gas device that has not been used for quite some time, pay attention to any smell of gas leakage.
  • Gas has a bad odor, but if you are unaware of how it smells, you can compare it to the smell of rotten eggs. Smell it before lighting the pilot.
  • If there is a smell of gas, propane, or any other flammable liquid, then avoid re-lighting the pilot. Modern heaters will prevent the lighting from occurring.
  • If you want to activate your machine because the pilot light failed, then look out for the root cause of the failure. Don’t turn the device back on if you have not solved the problem.
  • Determine if your unit is safe for re-lighting and if the relief valve is working appropriately.
  • If you have an electric tankless water heater, inspect it for clutter and naked wires. If they are present, don’t re-light your appliance until you have rectified it properly.
  • If your heater has been tripping off and you have tried to replace the fuse and reset the breaker, but nothing has worked, then you should get it serviced. After service, it will become as good as a new unit.
  • While activating the gas valve or illuminating the pilot light, keep your bare body and face at a distance from the opening. If you are not watchful and delayed lighting happens or maybe the pilot is out of position, you could get burned.  
  • Inspect the burner for dirt and rust before lighting the pilot light. If it is enclosed with dust and rust, avoid lighting it. It is better to get it serviced or clean it on your own.
  • Before turning on the gas valve, ensure first that external and internal covers are at the right location. 
  • If you are trying to activate the pilot and the burner is not kindling, don’t try to turn it on any further. At this point, you have to clear the gas. If you don’t know how to do this, hire a professional service.
  • Also, you can consult with the user manual that the manufacturer has provided you with the unit. If you are confused about any component or part, consult with the manual.
  • Pro Tip: Never throw away the manuals of any appliance or gadget you purchase because you never know when you will need its help. However, if you have lost it, get the brand’s name and your device’s model number and then surf the internet to find them out. You will find some useful information on their site.
  • Some companies place guidelines on the heaters, those may also help you to troubleshoot them.


Whether you are in a residential or commercial setting, you should make it a habit to regularly turn your heater on and off. It keeps it in tip-top condition and safe to use.
But if you are experiencing any technical glitches while activating it, you can quickly inspect it. When an issue occurs, your device displays an error code on the LCD, try to interpret it, but if you can’t do it, contact an expert.
After reading our article on “how to turn on water heater”, you should be able to activate it perfectly. If it turns on without any complications, it means its valves, sensors, heating component, and burner are working properly.

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