If your water heater is leaking, the first move is to shut off the water and the power or gas — a failed tank can dump 40-plus gallons onto the floor. Where the water is coming from tells you how serious it is: a drip from a fitting or the drain valve is often a repair, but water pooling at the base of the tank usually means the tank has corroded through and needs replacement. Use the triage tool below, then see our Bellevue water heater repair: tank, tankless, and heat-pump page. If it's actively flooding, that's an emergency plumbing call.
Pick where the water is coming from to see what it means.
This is first-aid guidance, not a diagnosis — a leak's real severity depends on the specific unit. When in doubt, shut it down and have it looked at.
The source of the leak tells you how serious it is. Water at the base of the tank usually means a corroded tank (replace it); leaks at the top connections, the T&P valve, or the drain valve are more often repairs.
Pooling under the tank: the inner steel tank has most likely rusted through. This isn't repairable and can fail suddenly — shut it down and plan a replacement.
Top connections: a loose or failed water/gas fitting or flex connector — frequently a straightforward repair.
Temperature & pressure relief (T&P) valve: it may be relieving excess pressure (a sign of overheating or thermal expansion that needs an expansion tank) or the valve is failing. Never cap this valve — it's a safety device.
Drain valve: often just a worn valve at the base — usually a minor fix. If you can't find a source at all, dry everything and recheck; condensation is common on gas units in cold weather.
It can be. The immediate risks are water damage from a tank rupture, electrical hazard on electric units, and — on gas units — the relief valve being capped or the unit overheating. Shut off the water and the power/gas if you see an active leak.
A full tank holds 40 to 80 gallons under supply pressure. When the tank wall finally goes, it empties fast and keeps refilling until the water is shut off — which is why catching a base leak early and shutting the supply matters. On electric units, water plus electricity is a shock hazard, so cut the breaker before mopping up.
Repair leaks at fittings, the drain valve, or the T&P valve, especially on a unit under about 8 years old. Replace when the tank itself is leaking, when the unit is past 10–12 years, or when the repair approaches half the cost of a new heater.
A tank leak is always a replacement — there's no fix for a corroded tank. For everything else, age is the deciding factor: a fitting leak on a 4-year-old heater is worth repairing; the same leak on a 13-year-old unit is a signal to replace before the tank goes too. Not sure how old yours is? Decode it with our water heater age calculator.
Ready for a real, written flat-rate quote? These are the services behind the estimates above:
Deeper background on what drives these prices:
Water at the bottom of the tank is most often the inner steel tank corroding through, which can't be repaired and means the heater needs replacement — it can also fail suddenly, so shut off the water supply. Less seriously, the leak could be coming from the drain valve at the base (a minor fix) or be condensation, so confirm the exact source before assuming the worst.
If it's a small drip from a fitting or the drain valve, briefly yes, but get it addressed quickly. If water is pooling under the tank, shut off the water and the power/gas and stop using it — a corroded tank can rupture. Never cap a leaking T&P relief valve to stop the drip; that defeats a safety device.
A tank that's leaking from the bottom can fail within days or limp along for weeks — it's unpredictable, which is why replacing it on your schedule beats an emergency flood. Fitting and valve leaks don't shorten the tank's life if repaired promptly. If the unit is already 10+ years old, a leak is usually the cue to replace.
Shut off the cold-water inlet valve on top of the heater (or your home's main shutoff), then cut the power at the breaker for an electric unit or turn a gas unit's control to off. Move valuables off the floor, and call a plumber — active flooding is an emergency, not a wait-until-morning issue.
