Why Is My Water Heater Leaking?

Quick Answer

Common sources of water heater leaks include: a failing temperature and pressure (T&P) relief valve, a worn drain valve, a loose fitting or union, or — for older tanks — corrosion in the tank itself. Condensation can look like a leak but usually isn't one. If you confirm a real leak, shut off the water supply and power/gas to the unit right away, since continuing to run a leaking water heater risks water damage and, in some cases, an electrical hazard.

Start With the Basics: Is It Actually Leaking?

Before assuming the worst, check whether the moisture around your water heater is condensation or an actual leak. Condensation is common on cold water lines or during humid weather and usually dries up on its own. Wipe the tank and surrounding fittings dry, then check back in a few hours — if moisture returns, you likely have a real leak somewhere in the system.

Common Causes of a Water Heater Leak

Common sources of water heater leaks include:

• Temperature and pressure (T&P) relief valve — this safety valve can release water if internal pressure builds up too high, or it may simply be worn and need replacing.
• Drain valve — located near the bottom of the tank, this valve can loosen or wear out over time.
• Loose fittings or unions — the connections where water lines meet the tank can loosen with age or vibration.
• Tank corrosion — over many years, the tank itself can corrode and develop a leak, which usually means the unit needs to be replaced rather than repaired.

What to Do Right Away

If you confirm an active leak, shut off the water supply to the unit at the cold water inlet valve. For electric water heaters, switch off the breaker; for gas units, turn the gas control to "off." This limits water damage and reduces safety risk while you sort out next steps.

Is It Safe to Keep Using a Leaking Water Heater?

Generally, no. Continuing to use a leaking water heater can allow the leak to worsen, cause water damage to flooring and nearby structures, and in some cases create an electrical safety hazard. It is worth addressing promptly rather than waiting to see if it gets better.

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