Why Water Heater Pilot Keeps Going Out - Your 7-Step Pro

There’s nothing quite like the shock of an ice-cold shower when you were expecting a steamy, relaxing one. You check your water heater, only to find that little blue flame—the pilot light—has vanished again. It’s a frustrating and all-too-common problem for homeowners.

I get it. As an HVACR technician, I’ve seen this exact scenario play out in countless homes. That flickering pilot is the heart of your gas water heater, and when it fails, your comfort fails with it.

But here’s the good news: I promise to help you solve this. This guide will walk you through exactly why your water heater pilot keeps going out and provide the clear, safe steps to diagnose the issue. Imagine having consistent hot water again, without the constant worry of relighting a pilot.

We’ll explore the most common culprits, from a simple dirty sensor to more complex ventilation issues, giving you the confidence to either handle the fix yourself or know exactly what to tell a professional. Let’s get that flame—and your hot water—back for good.

Understanding Your Water Heater Pilot Light: The Tiny Flame with a Big Job

Before we dive into troubleshooting, let’s quickly talk about what that little flame actually does. Think of the pilot light as the tireless security guard for your water heater. It’s a small, continuously burning flame that stands ready to ignite the main burner whenever the water temperature drops.

Working alongside the pilot light is a critical safety device called a thermocouple. The thermocouple is a metal rod that sits directly in the pilot flame. Its job is to sense the heat from the pilot light and, in response, generate a tiny electrical current.

This current tells the gas valve, “All clear! The pilot is lit, and it’s safe to release gas to the main burner when needed.” If the pilot flame goes out for any reason, the thermocouple cools down, the electrical signal stops, and the gas valve automatically shuts off all gas flow. This brilliant safety feature prevents raw, unburned gas from filling your home.

The Most Common Culprit: A Faulty or Dirty Thermocouple

In my experience, about 80% of the time a pilot light refuses to stay lit, the thermocouple is the troublemaker. It’s either dirty, bent out of position, or has simply worn out.

What is a Thermocouple?

As we just covered, the thermocouple is a heat-sensitive sensor. It’s a simple, inexpensive part, but it plays a massive role in your water heater’s operation and safety. When it fails, it fails “safe” by shutting off the gas, which is why your pilot won’t stay lit.

How to Tell if Your Thermocouple is the Problem

Here are the classic signs of a bad thermocouple:

The pilot light goes out the instant you release the control knob after holding it down for a minute.
The pilot flame is lit, but it’s a weak, yellow, or flickering flame that isn’t fully engulfing the tip of the thermocouple.
The thermocouple rod is visibly covered in soot or carbon buildup.

A Step-by-Step Guide to Cleaning Your Thermocouple

Sometimes, all your thermocouple needs is a gentle cleaning to restore its connection. If you’re comfortable with a little DIY, this is a great first step. This is one of the most effective why water heater pilot keeps going out tips you can try.

Safety First: Turn Off the Gas! Find the gas shut-off valve on the pipe leading to your water heater. The handle should be perpendicular to the pipe to be in the “OFF” position. Also, turn the control knob on the water heater itself to “OFF”.
Access the Burner Assembly. You may need to remove a metal cover plate at the bottom of the water heater. It’s usually held on by a couple of screws.
Locate the Thermocouple. You’ll see two thin lines running from the gas control valve to the pilot assembly. One is the pilot tube (carrying gas), and the other is the thermocouple (a thin copper line).
Gently Clean the Tip. Take a piece of fine-grit sandpaper, an emery cloth, or even the rough side of a dry sponge. Gently rub the top 1-2 inches of the thermocouple rod to remove any soot or corrosion. The goal is to make the metal shiny again.
Reassemble and Relight. Put the cover back on, turn the gas supply back on, and follow the procedure to relight your pilot light.

When to Replace the Thermocouple

If cleaning doesn’t work, the thermocouple has likely failed. The benefits of why water heater pilot keeps going out troubleshooting yourself can save you a service call fee, and this is a manageable replacement. They are inexpensive (usually under $20) and available at any hardware store. However, if you’re not confident in your ability to properly install the new one, this is a quick and easy job for a licensed professional.

Why Water Heater Pilot Keeps Going Out: 6 More Common Problems

If the thermocouple isn’t the issue, don’t worry. We have a few more culprits to investigate. Understanding these common problems with why water heater pilot keeps going out will help you pinpoint the source.

Problem #1: A Dirty Pilot Orifice

The pilot orifice is a tiny opening where the gas comes out to create the pilot flame. Over time, dust, lint, and soot can clog this opening, restricting gas flow. This results in a weak, lazy, and often yellow flame that isn’t hot enough to properly heat the thermocouple.

The Fix: With the gas turned off, you can sometimes clear this orifice by gently tapping the pilot tube or using a can of compressed air. For a more thorough cleaning, a technician will use a special tool or a very fine wire to clear the blockage.

Problem #2: Insufficient Air Supply or Drafts

Your water heater needs to breathe! Gas appliances require a steady supply of oxygen for proper combustion. If your water heater is in a small, sealed closet, it might be starving for air, causing the flame to extinguish.

Similarly, a strong draft from a nearby window, vent, or even a poorly sealed flue pipe can literally blow the pilot light out. This is a key part of any why water heater pilot keeps going out guide.

The Fix: Ensure the area around your water heater is clear of clutter. Check for and seal any obvious sources of drafts. If the room is too small, a technician may need to install vents to provide adequate combustion air.

Problem #3: A Failing Gas Control Valve

The gas control valve is the command center of your water heater. It houses the thermostat and the safety mechanisms. While durable, these valves can fail over time. If the internal safety magnet or valve is weak, it may not hold the pilot open even with a good thermocouple signal.

The Fix: This is not a DIY job. Diagnosing and replacing a gas control valve requires specialized tools and knowledge. If you suspect the valve is the issue, it is crucial to call a qualified technician.

Problem #4: A Clogged Flue or Vent Pipe

The flue pipe on top of your water heater is the exhaust system, safely venting harmful combustion byproducts like carbon monoxide outside. If this pipe becomes blocked by a bird’s nest, leaves, or other debris, the exhaust gases can’t escape.

This creates a dangerous backdraft that pushes the gases back down into the burner chamber, which will extinguish the pilot flame. This is a serious safety hazard.

The Fix: Call a professional immediately. A blocked flue can lead to carbon monoxide poisoning. A technician will safely inspect and clear the vent pipe.

Problem #5: A Tripped Thermal Switch

Many modern water heaters have a thermal cutoff switch (TCO) as an extra layer of safety. It’s a small, often resettable button located on the front of the burner assembly. If it detects excessive heat in the burner chamber (usually from a backdraft or poor combustion), it trips and cuts off the gas.

The Fix: You may be able to reset this switch, but a repeatedly tripping switch is a giant red flag. It means there is an underlying venting or combustion problem that needs to be addressed by a pro. This is one of the most important why water heater pilot keeps going out best practices: don’t ignore safety warnings.

Problem #6: Main Burner Issues

Sometimes, the issue isn’t the pilot itself, but the main burner. If the burner is dirty or clogged, it can cause a “rollout” or delayed ignition. When the gas finally does ignite, it does so with a small “whoosh” or explosion that can be forceful enough to blow out the pilot light.

The Fix: This points to a need for a thorough cleaning of the main burner assembly, a job best left to a professional to ensure it’s done correctly and safely.

A Step-by-Step Guide to Safely Relighting Your Pilot Light

Once you’ve addressed the potential problem, you’ll need to relight the pilot. Always approach this with caution.

IMPORTANT: If you smell a strong gas odor (like rotten eggs), STOP IMMEDIATELY. Do not use any electronics or create a spark. Leave the house, and call your gas company or 911 from a safe distance.

Read the Instructions. Every water heater is slightly different. The lighting instructions are almost always printed on a label on the side of the tank. Read them first.
Turn the Knob to “PILOT”. Locate the gas control knob on the front of the unit. Turn it from “ON” or “OFF” to the “PILOT” position.
Press and Hold. Push the control knob or a separate red button down and hold it. This manually sends a small amount of gas to the pilot orifice.
Light the Flame. While still holding the button down, use the built-in piezo igniter (a push-button that clicks) or a long-reach lighter to ignite the pilot flame. You should be able to see it through a small viewing window.
Keep Holding. Continue to hold the button down for a full 60 seconds after the flame is lit. This gives the thermocouple time to heat up and send its signal to the gas valve. This is the step most people rush.
Release and Turn to “ON”. Slowly release the button. The pilot flame should remain lit. If it does, turn the control knob to the “ON” position and set your desired temperature. You should hear the main burner ignite shortly after.

Best Practices for Pilot Light Maintenance: A Simple Care Guide

An ounce of prevention is worth a pound of cure, especially with your water heater. Following this simple why water heater pilot keeps going out care guide can prevent future headaches.

Regular Visual Inspections

Once a month, peek through the viewing window at your pilot flame. A healthy flame is a strong, steady blue color, sometimes with a tiny yellow tip. A weak, wavy, or mostly yellow flame indicates a problem with dirt or air supply.

Keep the Area Clear

Never store flammable materials, laundry, or general clutter around your water heater. It needs at least 6-12 inches of clear space on all sides for proper airflow and safety.

Schedule Annual Professional Maintenance

The best way to ensure a long, efficient life for your water heater is to have it professionally serviced once a year. A technician will clean the burner and pilot assembly, check the venting, test safety features, and replace the anode rod if needed. This is a smart, eco-friendly why water heater pilot keeps going out solution, as a clean unit runs more efficiently.

Frequently Asked Questions About a Failing Pilot Light

How much does it cost to fix a water heater pilot light?

The cost can vary widely. If the solution is a DIY thermocouple cleaning, it’s free. A replacement thermocouple you install yourself is under $20. A professional service call to diagnose the issue and replace a thermocouple will typically range from $150 to $300. More complex repairs like a new gas control valve can cost $400 or more.

Is it dangerous if my pilot light keeps going out?

Yes, it can be. While safety features are designed to prevent disaster, a pilot that repeatedly goes out is a symptom of an underlying problem. It could indicate poor venting, which can lead to a dangerous buildup of carbon monoxide in your home. Never ignore this issue.

Can I fix the pilot light myself?

Some fixes, like cleaning a thermocouple or ensuring the area is clear of drafts, are well within the reach of a capable DIYer. However, for any repair that involves opening up the gas line, replacing the gas control valve, or dealing with the venting system, you should always call a licensed professional.

Should I just replace my old water heater?

If your water heater is more than 10-12 years old and is starting to have frequent problems, replacement is often the wisest choice. A new, more efficient model can provide better performance and lower energy bills, making it a great sustainable why water heater pilot keeps going out long-term solution.

Tackling a pilot light issue can feel daunting, but with this guide, you’re now equipped to diagnose the most common problems safely. Remember to always prioritize safety, and don’t hesitate to call for professional backup when you need it.

Stay warm, stay safe, and enjoy that hot shower!

Author
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David Clark

Founder & Lead HVAC Specialist at HVACRLY

David Clark is the founder of HVACrly and a certified HVAC specialist with 10+ years working on residential and light-commercial systems. He turns complex heating, cooling, ventilation, and refrigeration topics into clear, actionable guides focused on safety and energy efficiency. When he’s not on a service call, he’s testing tools and writing step-by-step tutorials.