Why won't my water heater pilot light stay lit?

Before you touch the controls

If you smell gas, do not try to light anything. Leave on foot, avoid anything that can spark, including your phone, and call the gas utility and 911 from a safe place^[3].

If there is no gas smell, you can follow the lighting instructions printed on the label on your water heater. They are written for owners of standing-pilot models. Follow them exactly, in order. HomeGuide warns never to attempt a hand light on a unit with electronic ignition^[1].

How the pilot stays lit

On a standing-pilot gas water heater, a small flame burns all the time. A thermocouple (or on some models a thermopile) sits in that flame. When it is hot, it makes a tiny electrical signal that holds the gas control valve open. If the flame goes out or the sensor fails, the signal stops and the valve shuts off the gas. That is a safety feature: it keeps gas from flowing when nothing is burning.

So "it lights while I hold the button, then goes out when I let go" almost always means the valve is not getting that signal.

Standing pilot or electronic ignition?

Look through the small sight window near the bottom of the tank. A small blue flame that burns all the time means a standing pilot, and the lighting label applies. If there is no flame between heating cycles and the control has a status light, the unit uses electronic ignition. On those, a pilot that "won't stay lit" usually shows up as a blinking fault code instead. Write the blink pattern down, match it to the chart on the label, and call a pro rather than trying to light it^[1].

Causes, most to least common

Cause	Clue	Who fixes it
Worn or misaligned thermocouple	Lights, goes out the moment you release the knob	Licensed plumber
Dirty or clogged pilot tube	Weak, yellow or flickering pilot flame	Licensed plumber
Flammable vapor sensor lockout	Will not relight at all; status light shows a lockout	Licensed plumber, after fumes are removed
Blocked combustion air intake	Pilot goes out after running a while; lint or dust around the base	Pro to clean; homeowner keeps the area clear
Draft or venting problem	Pilot blows out on windy days or when other exhaust fans run	Licensed plumber (carbon monoxide risk)
Failing gas control valve	Thermocouple replaced and it still will not hold	Licensed plumber
Low gas supply	Other gas appliances also struggle	Gas utility or propane supplier

Flammable vapor sensors. Many newer gas tank water heaters have a sensor that shuts the burner down if it detects fumes from gasoline, paint thinner, solvents or similar products. Once it trips, the heater may not relight until a pro resets or replaces the sensor. If you store those products near the heater, move them to a detached shed or garage once you are sure it is safe.

Drafts and venting. A pilot that blows out repeatedly can mean the flue is blocked or air is being pulled down it. That same problem can let exhaust into the house. Scorch marks around the burner door are a sign. Shut the gas control off and call.

What a homeowner can do

• Follow the lighting label once or twice, no more.
• Keep the floor around the base clean and clear of lint, dust, boxes and stored chemicals.
• Note the flame color through the window when lit: a steady blue flame is normal; yellow and floppy suggests a dirty pilot.
• Note any pattern: windy days, when the dryer or a bath fan runs, after a new appliance was installed.

Do not remove the burner door, bend the thermocouple, clean the pilot orifice or work on the gas control yourself. Those are gas-train parts and belong to a licensed plumber.

Costs and the repair or replace question

HomeGuide's national ranges, published August 2025^[1]:

Repair	Typical range
Pilot light relight or replacement	$50 to $200
Thermocouple replacement	$100 to $325
Gas control valve replacement	$150 to $550

A thermocouple is a modest repair worth doing on most tanks. A gas control valve on an older unit is a closer call. Rheem's guidance: repair units under about 6 to 8 years old, consider replacement past 10, and replace when repair exceeds 50% of a new unit's cost^[2]. See repair or replace.

When to call a pro

• The pilot will not stay lit after one or two attempts.
• The status light shows a lockout or flammable vapor fault.
• The pilot flame is yellow, weak, or blows out on its own.
• Scorch marks, soot, or a smell of exhaust near the heater.