Gas water heater, no hot water. Probably the pilot. Smell first, then relight once.
Cold water is a nuisance. Gas is not. The smell test decides which one you have.
What is probably happening
- The pilot went out. A draft, a dirty pilot tube or a worn thermocouple does it.
- If it relights and goes out again within a day, the thermocouple (the sensor that proves the pilot is lit) is failing. Angi puts that repair at about $150 or less.
- If the pilot will not light at all, the gas valve may be closed or the utility may have interrupted supply.
Do this in the next five minutes
- Smell for gas at the heater. No smell, continue. Any smell, stop and go to the gas answer.
- Turn the gas control knob to Off. A. O. Smith's instruction is to wait at least 10 minutes so any gas in the lines can dissipate.
- Turn the knob to Pilot, press and hold it in, and click the igniter button about once a second for up to 90 seconds until the pilot lights or the status light shows.
- Keep holding the knob for the time the label on your heater says, then release slowly. Check the pilot stays lit.
- Turn the knob to On or your temperature setting. If it does not light or goes out again, stop and call.
Do not
- Do not relight if you smell gas. A. O. Smith: do not continue if you smell gas.
- Do not relight more than once or twice. If it will not hold, the part is failing and repeated attempts let gas accumulate.
- Do not use a lighter or match on a heater with an electronic igniter.
Who to call
A licensed plumber
Thermocouples, gas valves and pilot assemblies are plumber work. If the utility has shut the gas, the utility relights it.
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What it should cost
$228 to $1,017, averaging $616
Water heater repair, national range. Thermocouple about $150 or less. Thermostat $150 to $200
Source: Angi, water heater repair cost, updated August 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the plumbing page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Is it the thermocouple or the gas control valve, and how did you test?
- How old is the heater from the serial number, and would you repair it at that age?
- Will you check the flue draft and the burner while you are in there?
- Is the service call fee applied to the repair?
End the call if
- A replacement heater quoted before anyone has tried a $150 thermocouple.
- A plumber who relights it without checking why it went out.
- Anyone who tells you to keep relighting it yourself.