Water Heater Pilot Light Won’t Stay Lit — What to Check Before You Call

Quick Answer

A pilot light that won’t stay lit usually points to a worn thermocouple (the sensor that keeps the light burning). A bad thermocouple is a $200–$350 repair. Before calling, try relighting it using your heater’s instructions (hold the pilot button for 30–60 seconds while holding the lighter to the flame). If it lights but goes out again within 30 seconds, the thermocouple is failing. If it won’t light at all, the gas valve may be blocked or the pilot tube is dirty. Most issues are fixable; the worst case is a faulty gas valve ($400–$600 replacement).

Why This Is Happening

Your water heater uses a pilot light (a small, continuous flame) to ignite the main burner when you need hot water. The thermocouple is a heat sensor sitting in that pilot flame. When it detects heat, it sends a signal to the gas valve: “Pilot is lit, safe to flow gas.” If the pilot light goes out, the thermocouple cools, and the gas valve closes (safety feature).

A pilot light that won’t stay lit means one of three things:

The thermocouple is failing — Can’t hold the gas valve open. Most common (60% of cases)

Pilot tube is clogged — Dirt, sediment, or hard water mineral deposits block gas flow to the pilot. Common in Utah’s hard water (150–250 GPG). Cost to clean: $100–$200

Gas valve is stuck or faulty — Won’t stay open even with a working thermocouple. Least common, most expensive

Warning Signs to Watch For

Pilot relights but goes out within 30 seconds: Thermocouple is dying

Pilot won’t light at all, but you smell gas: Clogged pilot tube or gas valve problem

Pilot lights occasionally, but with a yellow flame instead of blue: Dust or sediment in the pilot tube

Smell of rotten eggs near the heater: Possible gas line issue. Call Enbridge immediately (1-800-333-4797)

Clicking sound but no ignition: Igniter is sparking, but the pilot tube is blocked

Safe Checks You Can Do Yourself

Step 1: Turn off the heater

Find the thermostat dial (usually at the bottom). Turn it to “Off” and wait 5 minutes to clear gas.

Step 2: Locate the pilot light assembly

Look at the bottom front of the tank:

Pilot light location

Thermocouple (thin metal tube)

Pilot tube (small gas line)

Step 3: Attempt a relight

Follow your heater instructions:

Turn the thermostat to “Pilot”

Hold the pilot/reset button

Press the igniter (or use a lighter)

Hold for 30–60 seconds

Release slowly

Turn the thermostat back to the normal setting

Outcome:

Stays lit → OK

Goes out within 30 seconds → thermocouple failing

Step 4: Check the thermocouple

If the light goes out:

Inspect for discoloration, bending, or damage

If damaged → replace (call plumber)

If it won’t ignite at all:

The pilot tube may be clogged

Cleaning possible but risky → plumber recommended

When This Becomes Dangerous

Stop immediately and call a professional if:

You smell rotten eggs (gas leak)

Gas smell after multiple relight attempts

Hissing or visible gas near the pilot assembly

Yellow/orange flame (incomplete combustion)

Carbon monoxide risk increases with malfunctioning combustion. If anything smells off, stop and call a professional.

What a Technician Will Do

Test the thermocouple with a multimeter

Replace thermocouple ($150–$250)

Clean pilot tube ($100–$200)

Inspect the gas valve and assembly

Relight and test for 30+ minutes

Check for gas leaks

Most visits result in thermocouple replacement.

Typical Repair Costs

RepairCostThermocouple replacement$150–$250Pilot tube cleaning$100–$200Gas valve replacement$400–$600Service call only$100–$150

Typical visit: $200–$350

Utah Hard Water Note

Wasatch Front hardness: 150–250 GPG

Mineral buildup clogs pilot tubes more often

Recurring issues → consider water softener ($500–$2,000)

Prevention: Stop Future Pilot Light Problems

Flush heater annually (Utah: every 6 months)

Consider a water softener for repeated issues

Keep the area around the heater clean (dust/debris)

Avoid hitting or disturbing the heater

Find Local Help

A pilot light that won’t stay lit usually means your thermocouple is at the end of its life. It’s a straightforward repair but requires a licensed plumber.

Salt Lake City: Water Heater Repair in Salt Lake City

Salt Lake County: Water Heater Repair in Salt Lake County

Browse all Utah cities: Find Water Heater Services Near You

Frequently Asked Questions

Why does my pilot light keep going out after replacement?
Likely a failing gas valve or defective replacement thermocouple.

Can I switch to an electric water heater instead?
Yes. No pilot light, but higher operating cost. Install: $1,200–$1,800.

Pilot light vs igniter: what’s the difference?

Pilot: always on (older units)

Igniter: sparks only when needed (newer units)

Is it safe to use the heater if the pilot won’t light?
No. Avoid repeated relighting attempts; gas can accumulate.

Do I need to replace the whole heater?
No. Replace the thermocouple unless the unit is 12+ years old or repairs are frequent.

Sources and Update Policy

This article was last updated in March 2026. Repair costs and availability change seasonally; we update quarterly.

Sources:

Utah water hardness data (USGS, Wasatch Front 150–250 GPG)

Enbridge emergency line: 1-800-333-4797

Manufacturer manuals (Rheem, AO Smith, Bradford White)