Water Heater Leaking: How to Find Where It Is Coming From
By Ray Bennett · Updated 18 September 2026 · 3 min read · Checked against the maker’s manual 
Dry the heater, put paper under it and wait an hour. Water coming from the top is a fitting you can fix. Water coming from the bottom of the tank usually means the heater has to be replaced.
A wet floor under a water heater does not tell you much on its own, because water runs down the tank and collects at the bottom no matter where it started. So the first job is finding the exact spot, not fixing anything.
Turn the gas or power off first
On a gas heater, turn the gas control to OFF, not to pilot. On an electric heater, switch off the breaker marked water heater. Then close the cold water valve on the pipe going into the top of the tank. That is the whole shutdown and it takes a minute.
The five places a water heater leaks
Check them in this order. The first four are parts you can replace. The last one is the tank itself.
The drain valve at the bottom
The tap near the floor. Wipe it dry and hold a tissue under it for a minute. Most of these drip because the washer inside has been nudged, not because anything is broken.
If this is wet: a $12 part, about 20 minutes, no plumber needed.
The T&P valve and its pipe
The lever on the side or the top with a pipe running down. If that pipe is wet, the valve opened because pressure or temperature got too high. That is a pressure problem, not a valve problem.
If this is wet: check the thermostat setting and the expansion tank.
The two pipes at the top
Dry both connections and the short pipes under them. A slow weep up here runs down the outside of the tank and collects at the bottom, which is what makes people buy a new heater they did not need.
If this is wet: a wrench, a rag and some thread tape.
Under the cover, from the tank seam
If everything above is dry and water still arrives at the floor, the tank has rusted through from the inside. There is no repair for this one.
If this is wet: replace the heater. Eight to twelve years is normal.
What the blinking light means
Gas heaters with an electronic control blink a status light, and the pattern is the fault. The common ones:
| Blink pattern | What the maker calls it | What it means |
|---|---|---|
| 1 flash | Normal operation | Nothing wrong with the control |
| 2 flashes | Thermopile low voltage | The pilot burns but is not making enough power |
| 4 flashes | Temperature exceeded | Water got too hot, which is what opens the T&P valve |
| 7 flashes | Gas control failure | The valve itself, and it needs replacing |
Questions people ask
Is a leaking water heater dangerous?
A slow drip is not. A swollen tank, or hot water forcing its way out, is. Gas plus water on the floor is also a reason to stop and call someone.
Can I keep using hot water while it drips?
For a day or two, with a bucket under it and the temperature turned down. Not longer, because the water reaches the floor and the wall.
How long should a water heater last?
Eight to twelve years on a gas tank, longer on electric if the anode rod was changed. After that, a leak from the bottom is the normal ending.
