How much does a water heater gas valve replacement cost?

The number

Fixr's repair guide: replacing a gas valve on a water heater costs between $150 and $300, labour included. Fixr's own note on the naming matters more than it looks: the gas valve is the same as the control valve, and the two terms can be used interchangeably.

That is why a plumber can quote you a "control valve" and a parts list can say "gas valve" for one and the same job.

Where it sits in the price list

For context, Fixr prices gas water heater repairs overall at $150 to $750, against $100 to $650 for electric, and attributes the difference to the extra components a gas unit carries: the burner, the gas control valve, the anode rod and the tank.

Why a gas unit has no separate thermostat

This Old House describes the control chain: gas-fired water heaters use a burner at the bottom of the tank, and a series of controls regulate the temperature and pressure, including thermostats, thermocouples and pressure relief valves, all working together to maintain peak water heating conditions and prevent potential hazards.

On almost every residential gas tank, that thermostat is not a separate box. The temperature dial you turn is on the face of the gas control valve, and the sensing probe runs from it into the tank. So on a gas unit, "the thermostat has failed" and "the gas valve has failed" are usually the same repair, priced at $150 to $300 rather than the $100 to $250 Fixr lists for an electric thermostat.

Telling it apart from the thermocouple

These two get mixed up constantly, and they cost almost the same, so the distinction is about not paying twice.

Our reading, marked as ours: the third and fourth rows are the ones that genuinely point at the valve. A pilot fault is not a valve fault, and swapping a valve because the pilot misbehaves is the most common way to spend $300 and fix nothing. Fixr publishes both prices; it does not draw this line.

The symptom you must not diagnose yourself

This Old House's safety guide is unambiguous on one point: if you smell gas, immediately evacuate the house and call your gas company or emergency services. The same guide lists a rotten egg smell as a possible sign of a gas leak.

A leaking gas valve is a gas leak, not a repair to research first. That is the case where the $150 to $300 question comes after the phone call, not before it. The rotten egg smell page covers how to tell a gas smell from a water smell, because they have completely different prices and completely different urgency.

When the valve is not worth replacing on its own

Fixr's own framing of a gas unit's weak points includes the tank, which it prices at $600 to $2,000 to replace. A gas valve at $300 on a tank that is rusting or already past its expected life buys time on a unit that is failing elsewhere. The repair or replace page does that arithmetic, and the repair cost hub has the full part-by-part table.