Gas Water Heater Pilot Light Problems — Causes & Fixes

Few plumbing problems get a phone call quicker than no hot water — and on a gas water heater, the culprit is usually a pilot light that won’t stay lit. After 40 years of plumbing work in Burleson, I’ve seen every variation of this problem. Most are simple to diagnose. Some are dangerous to mess with.

Here’s what every homeowner should know about gas water heater pilot lights — why they go out, how to relight yours safely, when a thermocouple needs replacing, and when to stop troubleshooting and call a plumber.

Gas Safety First

If you smell gas anywhere near the water heater: Leave the area immediately. Don’t operate any light switches or electrical devices. Call your gas company from outside or from a neighbor’s house. They will come out, usually for free, and shut off service if needed. Then call a plumber.

Common Pilot Light Problems

Pilot light won’t light at all — won’t ignite when you try
Pilot lights, then immediately goes out when you release the button — usually a bad thermocouple
Pilot burns weak or yellow instead of steady and blue
Pilot keeps going out after a few hours or days
No hot water at all even though the pilot appears lit

Why Pilot Lights Go Out

A few common causes:

Bad thermocouple — the metal probe sitting in the pilot flame. It senses heat and tells the gas valve “yes, the pilot is lit, keep gas flowing.” When it fails, the gas valve closes and the pilot dies. This is by far the most common cause.
Dirty pilot tube or burner — dust, spider webs, or lint can block gas flow to the pilot.
Drafts blowing out the flame — air leaks, vent issues, or a missing rain cap on the vent pipe outside the roof.
Bad gas valve — the control unit itself has failed.
Air in the gas line — happens after gas service work or a supply interruption.
Low gas pressure — usually a supply issue, not the water heater itself.
Tank is leaking water onto the burner — water heater is at end of life.

How to Safely Relight Your Pilot Light

Most gas water heaters have relighting instructions printed on a label on the front of the tank. The general process:

Tools you’ll need: Long-handled lighter (if your heater doesn’t have an electric igniter button)

Steps:

Turn the gas control knob to OFF. Wait at least 5 minutes for any residual gas in the area to dissipate.
Smell for gas near the bottom of the heater. If you smell anything, STOP. Don’t proceed. Call your gas company.
Turn the gas control knob to PILOT.
Press and hold the red or black reset button (sometimes labeled “pilot”) firmly.
While still pressing, ignite the pilot using the electric igniter button (if equipped) or insert a long-handled lighter into the pilot tube opening.
Once the pilot is lit, keep holding the button for 30–60 seconds. This lets the thermocouple heat up enough to signal the gas valve.
Release the button slowly. If the pilot stays lit, you’re done with this step. If it goes out, the thermocouple is likely bad.
Turn the gas control knob to ON. The main burner should fire when hot water demand is sensed.

If you’ve tried this 3+ times and the pilot still won’t stay lit, time to call.

When the Thermocouple Has Failed

If your pilot lights but won’t stay lit after releasing the button, the thermocouple is the most likely culprit. It’s a $15–$30 part. Replacing it is technically DIY-friendly on most gas water heaters:

Shut off the gas supply at the gas shutoff valve (usually on the line to the heater)
Disconnect the thermocouple from the gas valve (single nut, accessible from the front)
Remove the old thermocouple from the pilot bracket
Install the new one, making sure the tip sits directly in the pilot flame
Reconnect to the gas valve, restore gas, and relight following the steps above

However: this involves working with a gas connection. If you’re not comfortable with that, or if your heater is in a tight closet, call a plumber. A gas leak from an improperly tightened fitting is a real risk.

Other Causes to Check

If the thermocouple is good but the pilot keeps going out:

Check the vent cap on the vent pipe (usually on the roof). If it’s missing or damaged, wind can blow down the vent and kill the pilot.
Look at the pilot flame. It should be steady and blue with maybe a small yellow tip. A mostly yellow or orange flame means the pilot tube is dirty — needs cleaning.
Check the air supply. Gas water heaters need adequate combustion air. Tightly sealed closets can starve the burner.
Listen for the gas valve “clicking” when you turn the control knob. No click usually means the gas valve itself has failed.

When the Water Heater Itself Is the Problem

Sometimes the pilot problem isn’t really a pilot problem — it’s a sign the heater is at end of life:

Water leaking onto the burner — the tank has corroded through. Replace the heater.
Rust around the burner area — combustion chamber damage
Gas valve has burned out — sometimes replacing the gas valve costs almost as much as a new heater
Heater is 12+ years old with multiple recent issues — replacement is usually the smarter call

For a 15-year-old heater, the math usually points to replacement rather than another round of repairs.

When to Call a Plumber

Call us if:

The pilot won’t stay lit after thermocouple replacement
You smell gas anywhere near the heater — leave first, call the gas company first, then us
The pilot lights but the main burner won’t ignite — usually a gas valve issue
You see water around the base of the heater
You’re not comfortable working with gas connections
Your heater is more than 10 years old and giving multiple problems

A Word From Don

A gas water heater pilot light problem is almost always either a $20 thermocouple replacement or a sign the heater needs replacement. An honest assessment from a licensed plumber should tell you which one in 15 minutes — no upsell, no scare tactics.

If you’re in Burleson, Crowley, Joshua, Alvarado, Keene, Everman, or anywhere within about 20 miles of Burleson, give us a call. Same-day service on most plumbing calls. Free phone estimate before we head out.

Call Don: 817-447-2654