7 Warning Signs Your Water Heater Is Leaking

Water heaters rarely fail without warning. They whisper first — a damp spot, a rusty streak, a sound you can't quite place. Learn the seven early signs and you'll catch most leaks while they're still cheap fixes.

1. Water pooling at the base

The classic sign. Check whether the water returns after you dry it: wipe the floor, wait an hour, and look again. Water that reappears in the same spot is an active leak, not a spill.

2. Rust streaks running down the tank

Rust lines from a fitting or seam mean water has been escaping there for a while. Surface rust on the jacket is cosmetic; rust weeping from under a fitting or along a weld is not.

3. A hissing or sizzling sound

Water dripping onto a hot burner or element sizzles. If you hear hissing from the tank area with no obvious source, something is leaking onto something hot.

4. Hot water that runs out faster than it used to

A slow leak at the tank bottom lets cold water in continuously, diluting your hot supply. If showers got shorter over a few weeks, suspect a leak before you blame the thermostat.

5. Rusty or discolored hot water

Clear cold water but rusty hot water points to corrosion inside the tank — often the prelude to a shell leak. This is the moment to act, not after the tank splits.

6. A musty smell in the basement

In older New England basements, slow leaks evaporate off warm concrete before they ever form a puddle. The giveaway is a persistent musty or damp odor near the heater that air freshener can't fix.

7. The T&P discharge pipe is wet

That pipe running down the side of the tank should be bone dry. Moisture at its end means the relief valve is discharging — either from excess pressure or a failing valve. Both deserve prompt attention; see our T&P valve guide.

What to do when you spot a sign

Confirm it (dry-and-wait test), then shut the water and power to the unit if there's active pooling. For a full walkthrough, read what to do when your water heater leaks — and if anything looks urgent, our emergency team answers around the clock at (833) 713-2101.