Gas Water Heater Pilot Won't Stay Lit? Causes and When to Call

A pilot that keeps going out means cold showers until it is fixed, and it is one of the most common gas water heater calls we get in New Port Richey and Trinity. Most of the time the cause is a small part. Sometimes it is the heater telling you something bigger. Either way, gas appliances have a clear line between what a homeowner can safely check and what needs a licensed plumber.

First: if you smell gas

Do not try to relight the pilot. Do not switch lights or appliances on or off, and do not use a phone inside the house. Leave, and call your gas utility or propane supplier from outside. Once they have made it safe, call a plumber for the water heater.

Everything below assumes there is no gas smell.

How the pilot stays lit

On a standard gas tank water heater, the pilot is a small flame that lights the main burner when the water needs heating. A sensor called a thermocouple sits in that flame. As long as it is hot, it sends a tiny electrical signal to the gas control valve, which keeps the pilot gas flowing. When the flame goes out, the thermocouple cools, the signal stops, and the valve shuts off the gas. That is a safety feature.

So when the pilot lights while you hold the button but goes out as soon as you let go, the heater is usually telling you the thermocouple is not getting, or not reporting, enough heat.

The usual causes

A worn or misaligned thermocouple

Thermocouples wear out over time. They can also get bumped out of position so the flame no longer wraps around the tip. Either way, the gas valve does not get the signal to stay open. This is the most frequent cause of a pilot that will not hold, and it is usually a straightforward repair.

A dirty or weak pilot flame

Dust and debris can partly block the small pilot opening. A healthy pilot flame is steady and mostly blue. A weak, yellow or flickering flame may not heat the thermocouple enough. Cleaning or replacing the pilot assembly fixes it.

A blocked air intake on a newer sealed heater

Most gas tank water heaters made since 2003 have a sealed combustion chamber and a flame arrestor at the base. The U.S. Consumer Product Safety Commission explains that a voluntary industry standard, developed with the agency, called for tank-type gas water heaters manufactured after July 1, 2003 to carry this safety technology. The flame arrestor "prevents flashback fires by trapping and burning dangerous gas vapors inside of the heater."

The trade-off is that these heaters draw their air through a screen near the floor. In a garage, that screen collects dust, lint from a nearby dryer, leaves and pet hair. When it clogs, the flame does not get enough air and the pilot goes out. Some models also have a safety cutoff that shuts the heater down if it senses a problem in the combustion chamber, and that needs a professional to diagnose rather than a simple reset.

A gas supply problem

If the pilot will not light at all, or lights weakly, check the gas supply to the house:

• Propane homes: a low or empty tank is a common cause. Check the gauge, and call your supplier if it is low.
• Natural gas homes: check whether other gas appliances, such as a range, are working. If none are, the problem is the supply, not the heater.
• The gas shutoff at the heater should be fully open, with the handle in line with the pipe.

Drafts and venting

A strong draft can blow the pilot out, especially in an open garage on a windy day or where the vent cap is damaged. A vent that is blocked or disconnected is a safety issue, because exhaust gases need to leave the house. If you can see the vent pipe has come apart or is badly rusted, stop using the heater and call a plumber.

A failing gas control valve

If the thermocouple, pilot and air supply all check out and the pilot still will not hold, the gas control valve itself may be faulty. Replacing a gas control valve is licensed gas work.

What you can safely check

With no gas smell, a homeowner can:

1. Read the lighting instructions on the label on the heater. Every model is a little different.
2. Check that the gas shutoff to the heater is open and other gas appliances work, or check the propane gauge.
3. Look at the air intake screen near the base. If it is coated with lint or dust, turn the heater off and vacuum the outside of the screen gently.
4. Relight the pilot once, following the label exactly. Note whether it lights, how long it stays lit and what the flame looks like.
5. Clear stored items away from the heater, so air can reach it.

What not to do

• Do not keep relighting a pilot that keeps going out. Repeated attempts can build up gas in the combustion chamber.
• Do not tape, wedge or hold down the gas control button to keep the valve open.
• Do not remove, bend or bypass the flame arrestor, thermocouple or any safety cutoff.
• Do not store gasoline, paint thinner or other flammable liquids near the heater. The CPSC's guidance is blunt: "gasoline should never be stored or used indoors (in a basement or garage) where vapors can ignite."

When to call a plumber

Call for repair when:

• The pilot still goes out after one careful relight.
• The pilot will not light at all and your gas supply is fine.
• The flame is yellow, lazy or noisy.
• You see scorch marks, soot or rust around the burner door.
• The heater has a sealed safety cutoff that has tripped.
• There is water at the base of the heater as well as the pilot problem.

A licensed plumber tests the thermocouple and gas control, cleans or replaces the pilot assembly, checks the air intake and flame arrestor, and confirms the burner and venting are working safely. Our tank water heater repair service covers all of this for gas and electric tanks.

Repair or replace?

A pilot problem on a heater that is otherwise sound is usually a repair. It is worth talking about replacement when:

• The heater is near or past the end of its expected life.
• The tank is leaking or the burner area is badly rusted.
• The flame arrestor or combustion chamber is damaged, or keeps clogging.
• You have had several repairs in a short time.

Our guide to the signs you need water heater repair covers the other warning signs, and the water heater repair cost guide explains what drives the price of a repair. If replacement makes more sense, see water heater replacement in New Port Richey.

Gas water heater repair in New Port Richey and Trinity

Mr Water Heater repairs gas and electric tank water heaters across New Port Richey, Trinity, Port Richey, Holiday, Hudson and nearby west Pasco communities. Mark Lowrie holds Florida Master Plumber Licence CFC1433539, the business is licensed and insured, and 24/7 emergency service is available.

Call Mr Water Heater at +1 727 203 8201 or book tank water heater repair, and tell us the make of your heater and what the pilot does when you try to light it.