How much does a water heater thermocouple replacement cost?

Prices checked October 2026. Wages: BLS, May 2025.

A thermocouple is a safety sensor that makes its own electricity. Its tip sits in the pilot flame, and the heat produces a tiny voltage, measured in millivolts, that tells the gas control the pilot is lit. When the pilot goes out, the voltage drops and the control shuts off the gas. Thermocouples wear out, and the classic symptom is a pilot that lights but won't stay lit. On many newer heaters with flammable vapor ignition resistant (FVIR) designs, the thermocouple is part of a sealed pilot assembly that a plumber swaps as a unit, which costs more than a plain thermocouple.

The range above is for a plumber's visit to do that job on a standing-pilot gas water heater. It is built from the online list price of thermocouples (mostly generic Resideo parts, plus a brand pilot assembly at the top of the range) and about an hour and three quarters of billed time: 45 minutes hands-on and an hour for travel and diagnosis. The hourly rate comes from plumber wages in your area, multiplied to reflect a contractor's overhead and profit.

What moves the price

Plain thermocouple or full pilot assembly

Older heaters often take a generic thermocouple, one of the least expensive parts on any water heater. Many heaters with sealed combustion chambers use a brand-specific pilot assembly that includes the thermocouple or a thermopile and must be ordered by model number. That part costs several times more and takes longer to fit.

Getting the right diagnosis

A pilot that will not stay lit can also come from a partly blocked pilot opening, a dirty combustion air screen, a draft problem or a failing gas control. A plumber should confirm the thermocouple is the cause, often by measuring its output, before replacing it.

Combustion chamber access

On sealed-chamber heaters, the burner access door has a gasket that must be replaced correctly to keep the flammable vapor protection working. That care adds time and sometimes a small gasket kit.

Local plumber wages

Billed labor uses plumber pay at the 25th percentile, median and 75th percentile for your metro or state, with higher markup at the top end. A weekend no-hot-water call can land above the range.

Repair or replace?

A thermocouple or pilot assembly replacement makes sense on most gas water heaters that are not leaking. The part is small, and the rest of the heater may have years left. There are two exceptions. One is a heater near or past DOE's average life of about 14.5 years that shows rust or seepage. The other is when the plumber finds the real problem is the gas control valve, which costs much more. Either way, compare the repair to the replacement range on the gas water heater cost page. And don't keep relighting a pilot that keeps going out. Something is putting it out, and a plumber needs to find it.

Run the numbers for your unit.

What a complete quote lists

• What was tested (for example, thermocouple output in millivolts) and the finding
• Part replaced: generic thermocouple, or the brand pilot assembly by part number
• New burner door gasket if the heater has a sealed combustion chamber
• Relighting and a full heating cycle to confirm the repair
• Gas leak check at any fittings that were disturbed
• Service call fee
• Labor or flat repair price
• Parts and labor warranty terms

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