No Hot Water — Gas Water Heater Troubleshooting

A gas water heater that produces no hot water has usually lost its pilot light, has a faulty thermocouple, a failed gas valve, or a dirty burner. This guide walks through each cause in the order most likely to resolve the issue without professional help.

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   Step 1: Check the pilot light

   Look through the small sight window at the bottom of the water heater near the gas valve. The pilot light is a small, steady blue flame. If it is out, you need to relight it. Turn the gas valve dial to Pilot, press it in, hold it down, and use a match or piezo igniter to light the pilot flame. Keep the knob pressed for 60 seconds after the pilot lights, then slowly release. If the pilot stays lit, turn the dial to your desired temperature (usually 120°F).

2. 2

   Step 2: Test and replace the thermocouple

   The thermocouple is a safety device — a metal probe positioned in the pilot flame that generates a small voltage to hold the gas valve open. When it fails, the valve closes and the pilot cannot stay lit. To replace: shut off the gas supply valve, remove the burner access panel, unscrew the thermocouple from the gas valve (usually a simple push-and-turn connection) and from its bracket near the pilot. Install the new thermocouple, relight the pilot, and test.

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   Step 3: Check the gas supply

   Ensure the gas shutoff valve on the supply line to the water heater is fully open (handle parallel to the pipe). If you have other gas appliances, check whether they are working — if your stove also has no gas, the issue is with the gas supply to your home, not the water heater.

4. 4

   Step 4: Inspect the burner for blockages

   If the pilot lights and holds but the main burner does not ignite when you turn the dial to a temperature setting, the burner orifice may be blocked. Turn off the gas, remove the burner assembly, and clean the orifice and burner tubes with compressed air. Carbon buildup is common in older units.

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   Step 5: Replace the gas valve/thermostat (or call a pro)

   If the pilot holds and gas supply is confirmed but the main burner will not light, the combination gas valve/thermostat has likely failed. Replacement is possible as a DIY repair but involves working with gas connections — use Teflon tape or gas-rated pipe dope on all threaded connections and test for leaks with soapy water after reinstallation. If you are not confident working with gas, call a licensed plumber.