You go to take a shower, the water is cold, and when you check the garage the pilot light on your gas water heater is out. You relight it, and a day later it is out again. This is one of the most common gas water heater calls our team gets around Tampa Bay, and the cause is usually one of a few parts. Here is how a pilot system works, what makes it go out, and what you can safely check yourself before you call a plumber.
How the pilot and thermocouple work together
Most standard tank gas water heaters use a small, steady pilot flame to light the main burner whenever the tank calls for heat. Sitting in that pilot flame is a thin copper rod called a thermocouple (on some models it is a thicker thermopile). When it is heated by the flame, it makes a tiny electrical signal that tells the gas valve, “the pilot is lit, it is safe to keep gas flowing.”
If the pilot goes out, the thermocouple cools within a minute or so and the gas valve shuts off the gas. That is a safety feature, not a defect. It keeps unburned gas from filling your garage or closet. So when a pilot “won’t stay lit,” the question is always why the flame is going out, or why the valve thinks it went out.
Newer heaters may use electronic ignition and a flame sensor instead of a standing pilot. The idea is the same: no confirmed flame, no gas. If you are weighing gas against electric for your next heater, our gas vs. electric water heater guide covers the trade-offs for Florida homes.
The most common reasons a pilot keeps going out
- A worn or loose thermocouple. Thermocouples wear out over time. A weak one may hold the pilot for a few hours or days, then drop it. If it is bent out of the flame or loose at the gas valve, it will do the same thing.
- A dirty or partly clogged pilot. A small, weak, or yellow pilot flame often means dust, spider webs or debris in the pilot tube. A weak flame does not heat the thermocouple enough.
- A clogged flame arrestor screen. Heaters built since the early 2000s have a sealed combustion chamber with a screen on the bottom that lets air in but keeps flames from getting out. In Tampa Bay garages, that screen collects dust, dryer lint and pet hair fast. When it clogs, the burner starves for air and the pilot can go out.
- Drafts and poor venting. A strong breeze from an open garage door, a fan pointed at the heater, or a blocked or loose vent pipe can snuff out the pilot or pull exhaust back into the burner area.
- A failing gas control valve. If the thermocouple and pilot check out, the valve itself may not be holding. This is less common but does happen, especially on older units.
- Gas supply problems. If other gas appliances are also acting up, the issue may be the gas supply rather than the water heater. That is a call for your gas utility or a licensed plumber, not a do-it-yourself fix.
Safe checks you can do first
Before you do anything, use your nose. If you smell gas, do not relight anything, do not flip switches, and leave the house. Call your gas company from outside. Only continue with the steps below if there is no gas smell.
- Read the label. The lighting instructions are printed on the tank near the gas valve. Follow those exactly, since every model is a little different.
- Look at the flame. Through the sight glass, a healthy pilot is steady and mostly blue, and it wraps around the tip of the thermocouple. A small, lazy or yellow flame points to a dirty pilot or an air problem.
- Clear the area. Move boxes, paint cans, laundry and anything else stored against the heater. Keep at least a couple of feet clear around the base, and never store gasoline or chemicals near it.
- Vacuum the base. With the heater off and cool, gently vacuum dust and lint from around the bottom of the tank and the air intake openings. Do not take apart the sealed burner chamber.
- Check for drafts. Note whether the pilot goes out when the garage door is open or a fan is running. That pattern is a strong clue.
- Look at the vent. The metal vent pipe on top should be firmly connected and sloped up toward the roof. If it is loose, rusted through or disconnected, turn the heater off and call a plumber.
If the pilot relights and stays lit for a few days, keep an eye on it. If it goes out again, that usually means a part needs to be replaced or cleaned by a pro.
When to leave it to a plumber
Replacing a thermocouple, cleaning a pilot assembly, cleaning a flame arrestor or swapping a gas control valve all involve opening gas connections and the sealed burner area. Done wrong, they can cause gas leaks, burner rollout or carbon monoxide problems. That is work for a licensed plumber with a gas leak tester and the right parts for your model.
Our team checks the whole system on these calls, not just the part that failed: the pilot and thermocouple, the burner and flame arrestor, the gas valve, the vent and draft, and the tank itself. You will get a firm price before any work starts, with a qualified plumber on every job.
Repair or replace?
A thermocouple or pilot cleaning is usually a smart repair on a heater that is still in good shape. But if your tank is 10 or more years old, has rust at the base, is leaking, or the gas valve has failed, it often makes more sense to put that money toward a new heater. Our water heater repair and replacement page covers your options, and we will tell you plainly which way we would go if it were our home.
How to keep it from happening again
- Keep the base clean. A quick vacuum around the bottom of the heater every few months goes a long way, especially if it shares a garage with a dryer or pets.
- Flush the tank once a year. Sediment buildup makes the burner work harder and shortens the life of the tank. Our guide on how often to flush a water heater in Tampa explains why.
- Get a yearly check. Our maintenance plan is $150 a year and includes an annual visit where we look over your water heater, along with a free water test.
If your pilot keeps going out, or you are not comfortable relighting it, book online or call us at (813) 263-4941. We serve Tampa, St. Pete, Clearwater, Brandon, Riverview, Apollo Beach and the rest of Tampa Bay.
Pilot light won’t stay lit?
Northern Plumbing Co. is a licensed, master plumber-led team serving Tampa, St. Pete, Clearwater and the rest of Tampa Bay. You get a firm price before any work starts.