How to Turn Your Water Heater On

By Michael Franco

July 11, 2025

Whether you’ve just moved into a new house, finished a plumbing repair or turned your system off before a trip, there comes a time when you’ll need to turn on your water heater. It sounds simple, but water heaters vary. Some are gas, some are electric and others are tankless. Each type has its own quirks and safety steps. The good news is that once you understand the basics, you’ll be able to handle yours with confidence.

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Step 1: Make Sure the Tank is Full

It might sound obvious, but before switching on any water heater, always confirm that it’s filled with water. Turning on the heat in an empty tank can damage the heating elements or cause serious problems. To check, open the cold-water supply valve at the top of the tank. This is usually a lever or knob just above the heater. Let it run for a few minutes to fill the tank. Then, turn on a nearby hot water faucet. Once water flows steadily, without spitting or air bubbles, you know the tank is full.

Step 2: Know Your Type

The process differs depending on whether you have a gas or electric unit. Gas heaters rely on a pilot light and burner, while electric ones use heating elements powered through a circuit breaker. Tankless units are a category of their own, with electronic ignition and no storage tank. Take a moment to identify which you have. A gas water heater will have a gas line and a burner access door near the bottom of the unit (where the pilot light will be). If you see an electrical conduit and no burner, it’s likely an electric water heater.

Step 3: Turn It On

Electric Water Heater

First, check the water supply. Make sure the cold water valve is open, and the tank is full. Next, inspect the thermostat. Many electric heaters have a small panel with dials hidden behind covers. Set the temperature to a safe level, usually around 120°F. Once that’s done, head to your electrical panel and locate the breaker labeled “water heater.” Switch it to the ON position. The elements will begin heating the tank. Be patient, because electric elements take time – expect 30 to 60 minutes before you’ll have hot water, depending on tank size.

Gas Water Heater

Gas water heaters require a little more hands-on attention. Confirm the water supply first, then turn on the gas. Locate the shutoff valve on the line running to the heater and turn it so it’s parallel to the pipe. On the front of the unit, find the control knob with settings such as OFF, PILOT and ON. Turn it to PILOT and hold it there. This starts the gas flow to the pilot assembly. If your model has a push-button igniter, press it while holding the knob in the PILOT position until you see a flame through the viewing window. Older models may need a long match or lighter—carefully insert it while pressing the knob. Keep holding the knob for about 30 seconds after the flame appears so the thermocouple warms up. If the flame stays lit, turn the knob to ON and set the temperature. The main burner will fire as the tank calls for heat, and you’ll have hot water in about half an hour.

Step 4: Relighting the Pilot Light

Sometimes the pilot goes out on its own due to drafts, a dirty thermocouple or a temporary gas interruption. Relighting is the same process as starting a gas heater from scratch. Always switch the control knob to OFF for a few minutes to clear any lingering gas before attempting to light it again. If the pilot won’t stay lit after several tries, don’t force it – call a technician.

Turning on a Tankless Water Heater

Tankless models are the simplest to restart. Begin by checking the water supply to make sure the cold water line is open. Then turn on the gas valve or flip the circuit breaker if it’s an electric model. Finally, press the power button on the control panel. Select your temperature, and the unit will ignite automatically when water begins to flow. Because there’s no storage tank, you’ll have hot water within seconds.

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Safety First

Working with gas and electricity always requires caution. Sniff for gas before lighting a pilot; if you smell it, turn off the valve, leave the house and call your utility company. Check for leaks around the tank and pipes after you open the water supply. Use a safety tag if the heater is being serviced so no one turns it back on by mistake. And don’t crank the heat – anything above 120°F increases scalding risk and wastes energy.

How to Turn Off a Water Heater

Knowing how to shut your system down is just as important as starting it. For an electric unit, switch off the breaker in your electrical panel and close the cold water supply valve if you’ll be draining or servicing the tank. For a gas unit, turn the control knob to OFF, shut the gas valve so it’s perpendicular to the pipe and close the cold water supply valve if needed. For a tankless unit, simply power off at the control panel and shut the breaker or gas valve, depending on the model. Turning it off properly helps protect the unit and prevents accidental leaks or gas buildup.

Learn the Process

Turning on a water heater may feel intimidating the first time, but it’s just a sequence of careful steps: fill the tank, open the water supply, power or fuel it up and wait for the heat. With gas models, the pilot light is the only tricky part, but once you get the hang of lighting and relighting, it becomes second nature.

By learning the process, you’re not just getting hot showers back faster. You’re also keeping your home safer, avoiding costly damage to heating elements and giving yourself peace of mind. Water heaters don’t ask for much – just the occasional reset, relight or restart – so when you know how to do these simple steps, you’ll never be left guessing.

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