Water heater thermocouple replacement cost (2026)

On a gas water heater with a standing pilot, the thermocouple is a thin metal probe that sits in the pilot flame. It proves the pilot is lit so the gas valve will keep gas flowing. When it wears out, the pilot will not stay lit.

Figures are 2026 national estimates compiled from published cost guides such as HomeGuide, Angi and HomeAdvisor. Labor rates in high-cost metro areas often run above these ranges.

Typical costs

Symptoms of a bad thermocouple

• The pilot lights while you hold the button but goes out when you release it
• The pilot goes out repeatedly
• No hot water with the pilot out

It may not be the thermocouple

Many newer gas tanks use a thermopile and an electronic gas control instead of a simple thermocouple, and a status light flashes codes. On those, a dirty pilot, a weak thermopile, a clogged air intake or flammable vapor protection can all put the pilot out. Check your model before buying parts; our A. O. Smith status light off page covers one common control.

DIY or pro?

A standard thermocouple swap is one of the more DIY-friendly gas repairs, with the gas valve off and the manufacturer's instructions followed carefully. Sealed combustion chambers with flammable vapor protection make the job harder, and damaged door gaskets must be replaced. If you are unsure, hire a pro.

Not sure how old your heater is? The serial number tells you. See our guides for Rheem, A. O. Smith and Bradford White, and use our repair or replace water heater calculator to see how age changes the math.

Thermocouple, thermopile or flame sensor?

Knowing which one your heater uses avoids buying the wrong part. The model number on the rating label tells a parts counter or technician exactly what fits.

Try this before paying for a repair

1. Follow the lighting instructions on the heater's label exactly, including how long to hold the pilot button.
2. Make sure the gas supply valve to the heater is fully open.
3. Look at the pilot flame through the sight glass. A weak, yellow or wavering flame can point to a dirty pilot rather than a bad thermocouple.

If the pilot still will not stay lit, the thermocouple is the likely culprit, and the repair is usually quick. A pilot that goes out again soon after a new thermocouple points to drafts, venting or combustion air problems.

Getting a fair price

• Ask for a flat price that includes the part, labor and the service call.
• Ask the technician to show you the reading or the failed part that proves the diagnosis.
• Check the heater's age from the serial number. A repair on a heater past about ten years deserves a second look.
• Check the warranty first. Parts are often covered longer than labor.