Gas Water Heater Not Working? Common Causes and How to Fix It

When your gas water heater, a household appliance that heats water using natural gas or propane. Also known as a gas-fired water heater, it’s one of the most relied-on systems in your home—until it suddenly stops delivering hot water. If you turn on the tap and get cold water instead, you’re not alone. Gas water heaters don’t just break randomly. They fail because of predictable issues: the pilot light goes out, the thermocouple wears out, the thermostat fails, or sediment chokes the bottom of the tank. These aren’t mysterious problems—they’re everyday ones that happen to millions of homes.

Most gas water heater failures start small. A weak pilot flame, a dirty burner, or a thermostat that’s lost its calibration. You might hear a clicking sound but no flame. Or maybe the water runs hot for a few minutes, then goes cold—that’s usually a sign the thermostat isn’t holding the temperature. Sediment buildup is another silent killer. Over time, minerals in the water settle at the bottom, insulating the heating element from the water. That forces the heater to work harder, wear out faster, and eventually quit. If your heater is older than eight years, this is almost guaranteed. And if you haven’t flushed the tank in two years, you’re already running on borrowed time.

Fixing a gas water heater isn’t always a job for a pro. You can relight the pilot light yourself with the instructions on the unit. You can test the thermocouple with a multimeter. You can even flush the tank with a garden hose—no special tools needed. But if the gas valve is leaking, the burner assembly is cracked, or the tank is rusting through, those are red flags. No DIY fix will save you then. You’ll need a replacement. The good news? Most gas water heater issues are caught early. You don’t need to wait until your shower turns icy to take action.

Below, you’ll find real fixes from real homeowners who’ve dealt with the same problem. Some posts show you how to check the thermocouple without calling a technician. Others explain why the pilot light keeps going out after you light it. There’s even one on how to tell if your heater is beyond repair—so you don’t waste money on a repair that won’t stick. Whether you’re trying to save a few bucks or just want to understand what’s happening, these guides cut through the noise. No fluff. No jargon. Just what actually works.