Gas Water Heater

Gas-specific behavior worth understanding:

• The pilot that will not stay lit. Almost always the thermocouple ending its service, the safety part that proves flame exists. Routine to replace, and pointless to fight repeatedly.
• Soot, odd flame color, scorch marks. Combustion signatures: a starved or dirty burner, spillage at the draft hood. These are the signs that earn immediate attention on any fuel-burning appliance.
• Rumbling and popping from the tank. Water flashing to steam under a sediment blanket on the burner-heated bottom. It is the hard-water tax on gas units specifically, and the case for flushing.
• Recovery that slows over years. The same sediment insulates water from flame; a unit that once kept up and now lags is often burning gas into a mineral layer.

This page is the system view for gas units: how they work, what their gas-specific ownership questions are, and how to think about sizing and venting. When one is failing right now, the water heater repair page owns the fault trees; the tank-versus-tankless decision lives on the tank water heaters and tankless pages.

What shapes a gas unit's life:

• Combustion needs air and exhaust. A gas heater breathes: combustion air in, flue gases up and out. Closets sealed tight in renovations and flues serving drafty paths are where gas units get into trouble.
• Sediment hits gas units hardest. The flame heats the tank bottom, so mineral fallout lands exactly on the heat path; efficiency and tank life both pay.
• The anode decides the tank's age. Fuel aside, tanks die of corrosion, and the sacrificial anode is the part that decides when. Its condition matters more than the brand on the jacket.
• Code moves under old installs. Venting rules, drain pans, seismic strapping where required, expansion tanks on closed systems: replacements inherit today's code, which is why swap quotes include items the old install never had.