How much does it cost to replace a water heater gas control valve?

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

The gas control is the box on the front of the heater with the temperature dial. It senses water temperature, runs the pilot and main burner, and shuts off gas when something is wrong. On many models it also holds a high-temperature cutoff. A.O. Smith's guide for one direct-vent model says that once that energy cut off trips, it cannot be reset and the valve must be replaced. A control that has been wet, in a flood for example, should also be replaced. This is the most expensive common repair on a gas water heater, so the repair-or-replace question is a real one here.

The range above is for a licensed plumber to replace that valve (also called the gas valve or thermostat) on a 40 or 50 gallon gas tank water heater. It adds the online list price of brand and Resideo replacement valves from retailer listings to two and a half hours of billed time: about an hour and a half hands-on and an hour for travel and diagnosis. Labor is priced from local plumber wages, multiplied to cover the contractor's overhead.

What moves the price

Brand part versus trade replacement

Manufacturers sell their own valves, and Resideo makes trade replacements that fit several brands, such as its WT8840 for certain A.O. Smith, Bradford White and Rheem heaters. Prices vary by brand and model, and the right part depends on the heater's model number and gas type.

Labor time

The job means shutting off gas and water, partly draining the tank, removing the old valve, and fitting the new one with the pilot and burner connections. Then comes a leak test and a full heating cycle. All of that is why the model allows more hands-on time here than for most parts.

Diagnosis

A heater that will not heat or keeps shutting down can have a bad thermocouple or thermopile, a dirty pilot, a draft problem or a tripped flammable vapor sensor. A plumber should rule those out, since they cost much less than a new valve.

Your area's plumber wages

The labor part uses 25th percentile, median and 75th percentile plumber pay for your metro or state. With two and a half billed hours, regional wages move this repair more than a quick part swap.

Repair or replace?

Compare this repair to the gas water heater replacement range for your area before you say yes. On a heater under about seven years old with a dry, sound tank, a new valve usually makes sense. On one approaching DOE's average life of about 14.5 years, the valve and labor can come to a large share of a new installed heater, and the tank behind it is still old. Most homeowners in that spot are better off replacing the whole heater, which also resets the warranty. Check the manufacturer's warranty first. Gas controls are sometimes covered longer than labor, and that changes the math.

Run the numbers for your unit.

What a complete quote lists

• Diagnosis showing why the valve failed (for example, a tripped energy cut off, no output, water damage)
• Valve part number, gas type (natural gas or propane) and whether it is a brand or trade replacement
• Draining and refilling the tank
• Gas leak test on all disturbed connections
• Setting the temperature and running a full heating cycle
• Service call fee and labor or flat price
• Whether the part was covered by the heater's warranty
• Warranty on the new valve and on labor

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