How-To · Last updated September 28, 2026
Dry the floor around the tank, then check it again after an hour. If water comes back, look at four places in order: the connections on top, the pressure relief valve and its discharge pipe, the drain valve near the bottom, and the tank itself. Water at the fittings or valves is usually repairable; water coming from the tank body almost always means replacement.
Rust showing up in your hot water, or streaks running down the outside of the tank — either one points to corrosion happening inside. That's the tank itself failing, not a fitting or a valve.
Even a small amount of water collecting under or around the tank is worth checking. Dry the spot, wait an hour, look again. Comes back? Something's actively leaking.
That popping noise is sediment sitting at the bottom of the tank, and it's not a leak by itself — but it wears the tank down faster and often shows up right before one starts.
Most tank water heaters last 8 to 12 years. Past the decade mark, tank corrosion becomes the most likely explanation for almost any symptom on this list.
Where the water's coming from actually narrows down what's wrong, and it's worth checking before you call anyone.
Usually points to the inlet or outlet fittings where the cold and hot water lines connect, or a failing temperature-and-pressure (T&P) relief valve on top of the tank. Both are often repairable without replacing the whole unit — a loose fitting can sometimes just need re-tightening, though a failing T&P valve should be replaced, not ignored, since it's a safety component.
More often means trouble. This can be the drain valve (sometimes fixable) or, more seriously, corrosion inside the tank itself that's let go — which means replacement, not repair. Water pooling under the tank with no clear source at the fittings above it is the classic sign the tank itself is failing.
A water leak on its own isn't usually an immediate safety emergency — but a gas water heater adds a separate risk worth understanding clearly. The water leak and a gas leak are two different problems that can coincidentally show up around the same unit, and it's important not to assume one explains the other.
Signs of a possible gas issue — a sulfur or rotten-egg smell, a hissing sound near the gas line, or a pilot light that won't stay lit — are not something to investigate yourself. If you smell gas, leave the house and call your gas utility's emergency line from outside, before doing anything else, including flipping light switches. A water leak alone, without any gas smell or hissing, is not a carbon-monoxide or gas-leak emergency by itself — but if there's any doubt, treat it as one rather than guessing.
Condensation is moisture from the air collecting on something cold, so it follows the weather and the heating cycle. A leak is water escaping from inside the tank or plumbing, so it keeps coming back whatever the weather does. Dry everything with a towel and check again after an hour, then use this table.
| What you see | Condensation | Leak |
|---|---|---|
| Where the water is | Beads on the tank jacket or on the cold inlet pipe | Pooling at the base, dripping from a fitting, or running from a valve |
| When it appears | Humid days, or while a fresh tank of cold water heats | Any time, including dry weather and after the heater has been idle |
| After you dry it | Stays dry or returns only in small beads | Wet again within the hour |
| Other clues | Clear water, no rust | Rust trails, stains, mineral crust, rumbling or a dropping hot-water supply |
If you can't settle it, treat it as a leak. A sensor in the pan under the tank settles the question without guessing: it alarms when water actually collects, which a few condensation beads rarely do. Our water heater leak detector guide covers sensors, pans and automatic shutoff kits.
Nobody checks the water heater closet daily — which is exactly why a slow leak in there can run for weeks before the smell or the stain gives it away. That makes it one of the highest-value spots in the house for a point sensor. See our water heater leak detector guide for sensors, drain pans and automatic shutoff kits, or our general leak detector guide for options that alert your phone the moment water touches the floor.
FAQ
Dry the floor around the tank and check again after an hour. If water returns, check the top connections, the pressure relief valve and its discharge pipe, the drain valve, and finally the tank itself. Water from the fittings or valves is usually repairable; water from the tank body usually means replacement.
A small amount of condensation can be normal, but any leak from the tank body itself means it's failing and should be shut off, not kept in use.
Typically 8 to 12 years. Past 10 years, corrosion becomes the most likely explanation for a new leak.
Yes — shutting off the cold water supply and power or gas is a safe first step that limits damage while you wait.
It does — top usually means fittings or the pressure relief valve, often repairable. Bottom more often means internal tank corrosion, which means replacement.
A water leak alone usually isn't a gas emergency, but any sulfur smell or hissing near the gas line is a different problem — leave the house and call your gas utility, don't investigate it yourself.