Why is my water heater not making hot water?

No hot water feels like a dead water heater, but the tank itself is rarely the culprit. On gas units, the usual suspects are the pilot assembly and thermocouple — the safety device that shuts gas off when it cannot prove a flame. On electric units, heating elements and thermostats fail far more often than tanks. All of these are stocked-truck parts and modest repairs.

Partial hot water tells its own story. Water that starts hot and dies fast on an electric unit usually means the lower element failed — you are running on half the tank. Lukewarm-at-best often points at a thermostat. And water that has been slowly declining for months in our hard-water area is frequently sediment, which blankets the tank floor and steals both capacity and efficiency.

The one symptom that does end tanks: water weeping from the tank body itself. Fittings, valves, and the T&P relief valve can all be repaired — but a corroding shell cannot. If the tank is leaking from the tank, the conversation becomes replacement, and the useful move is getting ahead of it on your schedule instead of the tank's.