Everything that can go wrong with a tank or tankless water heater — and how to fix it. Our water heater guides cover leaks (from the bottom or the top), no hot water, pilot and ignition problems, relief valve issues, and real 2026 repair-vs-replace costs. Each guide separates safe DIY steps from work that needs a licensed plumber.
Last updated: July 2026 · Reviewed against Rinnai, Navien and Noritz service documentation Most tankless water heater problems trace back to three things: scale buildup, a clogged inlet filter, or a venting/ignition fault — and the unit will usually tell you which with an error code on its display. Unlike a tank heater, a tankless … Read more
Last updated: July 2026 · Based on A.O. Smith serial number dating conventions To find the age of an A.O. Smith water heater, read the first four digits of the serial number: the first two are the year and the next two are the week of manufacture. A serial number starting with 1542 means the … Read more
Last updated: July 2026 · Reviewed against A.O. Smith and Rheem service documentation Replacing a water heater thermocouple is one of the most common gas water heater repairs — and one of the cheapest. If your pilot light lights but goes out the moment you release the control dial, the thermocouple is almost certainly the … Read more
Last updated: July 2026 · Reviewed against A.O. Smith and Rheem service documentation Have a tankless unit? See tankless water heater repair instead. No hot water at all usually means a total failure: a gas water heater with its pilot out, or an electric one with a tripped breaker or failed heating element. Not enough … Read more
Last updated: July 2026 · Reviewed against A.O. Smith and Rheem operating instructions If your gas water heater has no hot water, the pilot light is the first thing to check — if it has gone out, the burner cannot fire. Relighting it is usually a simple DIY job, but if the pilot will not … Read more
Last updated: July 2026 · Reviewed against A.O. Smith, Rheem and Bradford White service documentation A leaking water heater has five likely sources, and where the water is coming from tells you how serious it is. A leak from the drain valve or a connection is a cheap fix. A leak from the T&P relief … Read more
Last updated: July 2026 · Reviewed against A.O. Smith, Rheem and Bradford White service documentation A water heater leaking from the drain valve is one of the most common and least expensive water heater leaks to fix — often for under $15. The drain valve is the spigot at the base of the tank used … Read more
Last updated: July 2026 · Reviewed against A.O. Smith and Rheem operating instructions To turn off a water heater, you need to stop two things: the power or gas that heats the water, and the cold water flowing into the tank. The exact steps depend on whether you have a gas or electric unit. This … Read more
Last updated: July 2026 · Reviewed against Watts and Cash Acme valve documentation and plumbing code guidance A leaking T&P (temperature & pressure) relief valve is either doing its job or worn out — and telling the difference matters, because one is a safety system working correctly and the other is a simple part replacement. … Read more
Last updated: July 2026 · Reviewed against A.O. Smith, Rheem and Bradford White service documentation Water pooling on top of your water heater is one of the more reassuring places to find a leak — because unlike a leak from the tank body, a top leak is almost always repairable and rarely means you need … Read more