How to light a gas water heater
Lost hot water after a pilot went out? Relight it safely, set the right temperature, and know the warning signs that mean it is time to call a pro.
Written by Illyrian Plumber
Expert ReviewedLicensed Master Plumbers
NJ Licensed Master Plumber | 10+ Years Experience | Serving Middlesex County, NJ
Safety first
If you smell gas, do not try to light the heater. Leave the house, do not use switches or phones inside, and call your gas utility from outside, then a licensed plumber. A rotten-egg odor means gas is present and lighting anything is dangerous.
When a gas water heater loses its pilot flame, the hot water stops, and relighting it is usually a five minute job you can do safely by following the steps below. This guide also covers setting the temperature and turning the unit off. If the pilot will not stay lit or you are uneasy working with gas, our water heater repair team handles it across Middlesex County. Work slowly and follow the lighting instructions printed on a label on your specific heater, since models vary.
About Illyrian Plumber
Licensed master plumbers serving Middlesex County, NJ since 2010. We specialize in water heater repair, water heater replacement, tankless water heater installation, and 24/7 emergency plumbing across East Brunswick, Edison, Sayreville, Old Bridge, Monroe Township, South Brunswick, and North Brunswick.
How to light or relight the pilot
Modern heaters use a push-button piezo igniter, so you rarely need a match. Read the label on your unit first, then follow these steps.
Step 1: Turn off the gas and wait
Turn the gas control knob to Off and wait a full five minutes. This lets any unburned gas clear out of the chamber so it is safe to light. Do not rush this step. If you smell gas at any point, stop and follow the safety notice above.
Step 2: Set the knob to Pilot and ignite
Turn the knob to Pilot, press and hold it down to send gas to the pilot, and press the red igniter button repeatedly until the pilot flame lights. On older units without an igniter, hold a long lighter at the pilot opening while pressing the knob.
Step 3: Hold, then switch to On
Keep holding the knob down for about 30 seconds after the pilot lights. This warms the thermocouple so it keeps the gas valve open. Slowly release the knob. If the pilot stays lit, turn the knob to On and set the temperature. If it goes out, repeat once, then see the troubleshooting section.
How to adjust the water heater temperature
The temperature dial is on the front of the gas control valve. Many dials show Low, Hot, A, B, C, and Very Hot instead of numbers. To turn the hot water up, rotate toward Hot or Very Hot, and to lower it, rotate toward Low.
Set it to about 120 degrees Fahrenheit. The US Department of Energy recommends 120 degrees to balance scald safety, bacteria control, and energy savings. Since the dial is not precise, run the hot water at a faucet for a minute and check it with a thermometer, then nudge the dial and recheck after a couple of hours.
If you constantly run out of hot water even at a higher setting, the tank may be undersized or failing. Our guides on how long a water heater takes to heat up and signs your water heater is dying can help you tell the difference.
No hot water and the pilot won't hold?
Our water heater techs serve Middlesex County, 24/7.
How to turn the water heater off
For everyday purposes, turning the gas control knob to Off shuts the heater down. For service, a leak, or a long absence, take two more steps.
- Turn the gas control knob to Off.
- Close the gas shutoff valve on the supply line near the heater by turning the lever so it crosses the pipe.
- If you are draining the tank, close the cold water inlet valve on top and connect a hose to the drain valve.
If you are shutting the heater because the whole house water is off, our water shutoff guide walks through the rest of the steps. Never let an electric or gas tank keep heating when it has no water in it.
When to call a plumber
Call a licensed plumber if the pilot lights but will not stay lit after two tries, which usually points to a worn thermocouple, if you smell gas, if you see water pooling under the tank, if the burner makes loud popping or rumbling sounds, or if the water never gets hot enough despite a correct setting. Gas components and venting affect safety, so they should be serviced by a professional.
Our team repairs pilot, thermocouple, gas valve, and venting issues through our water heater repair service, and when a tank is past its service life we handle water heater replacement across Middlesex County.
Frequently asked questions
How do I relight the pilot on a gas water heater?
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Turn the gas control knob to Off and wait five minutes for any gas to clear. Set the knob to Pilot, hold it down to release gas to the pilot, and press the igniter button until the flame lights, then keep holding for about 30 seconds. Release the knob, confirm the pilot stays lit, and turn the knob to On. If your heater has a sealed chamber, follow the lighting label printed on the unit.
What temperature should I set my water heater to?
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Set the water heater to 120 degrees Fahrenheit. The US Department of Energy recommends 120 degrees to prevent scalding and reduce standby energy loss, while still being hot enough for daily use. The thermostat dial on a gas heater often shows Low, Hot, A, B, C, or Very Hot rather than numbers, so 120 degrees usually falls around the Hot or A-B setting. Test the water at a tap and adjust from there.
Why won't my water heater pilot light stay lit?
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The most common cause is a worn thermocouple, the safety sensor that shuts off gas if it does not detect the pilot flame. A dirty pilot orifice, a loose thermocouple connection, or a tripped gas valve can also be the issue. If the pilot lights but goes out as soon as you release the knob, the thermocouple is the likely culprit and should be replaced by a licensed plumber.
How do I turn off a gas water heater?
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To turn it off normally, set the gas control knob to Off. To shut it down for service or a leak, also close the gas shutoff valve on the supply line near the unit and close the cold water inlet valve on top of the tank. Never leave a gas heater running if you smell gas. Leave the house and call your gas utility first, then a licensed plumber.
Water heater trouble in Middlesex County?
From pilot and thermocouple repairs to full replacements, our licensed plumbers serve East Brunswick, Edison, and all of Middlesex County, NJ.