Short answer
A water heater that leaks slowly is usually leaking from a fitting or a valve, and those are repairs. Dry the whole unit, then check three places: the connectors on top, the T&P discharge pipe on the side, and the drain valve at the bottom front. If every fitting stays dry and water keeps appearing under the tank, the tank has rusted through and the heater gets replaced. A leaking tank is never repaired, at any age.
Tell a fitting leak from a failed tank in 30 minutes
- Wipe the whole heater dry. Dry the top, the sides, the valves and the floor around the base.
- Lay paper towel or flat cardboard under the heater and around its base.
- Close the cold-water shutoff above the heater. Leave every tap in the house closed.
- Watch the water meter for 15 minutes. If the meter stops moving, the leak is at the heater or past it, not in the pipe feeding it.
- Look at the two connectors on top of the tank. Run a finger under each one and check for a bead of water forming again.
- Find the T&P valve on the side or top, with a pipe running down toward the floor. Feel the open end of that pipe for drips.
- Check the drain valve at the bottom front. A slow weep here wets the floor directly under the valve.
- Come back in 30 minutes and read the paper towel. Note which spot is wet and whether the wet spot is under a fitting or under the tank.
- Hire for this if the heater runs on gas. Do not loosen any fitting on the gas line or the vent. If you smell gas, leave the house and call the gas utility from outside. On an electric heater, turn the breaker off before touching anything near the top access panels.
If a fitting, the T&P pipe or the drain valve is wet and the rest is dry, you have a repair. If the paper under the tank is wet with every fitting dry, the tank is leaking and the heater gets replaced.
Repair or replace
| Situation | What to do |
|---|---|
| Water at a connector or union on top of the tank | Repair. The fitting gets opened, cleaned and resealed, or the flex connector gets replaced. |
| T&P discharge pipe dripping, tank in good shape | Repair. The plumber checks house pressure and replaces the valve. High pressure needs an expansion tank too. |
| Drain valve at the bottom weeping | Repair. The valve gets replaced or capped. |
| Water under the tank with every fitting dry | Replace. The tank has rusted through and no patch holds. |
| Tank over 10 years old with any leak at the tank | Replace. Expect a new unit rather than a repair visit. |
| Tank under 5 years old and leaking at the tank | Replace, and check the warranty first. Most tanks carry 6 years and the serial number carries the build date. |
| Water appearing on a wall or ceiling near the heater, not on the heater | Repair, but as a pipe leak. The heater is not the source. |
Can I do it myself?
You can find the leak yourself, and that is the part that saves money. Drying the unit, reading the paper towel and watching the meter take 30 minutes and tell a plumber exactly where to start. Tightening a loose drain valve cap is also fair game.
Hire for the fix itself. Opening a connector on a live water heater, replacing a T&P valve or swapping a tank involves hot water under pressure, and on a gas unit it also involves the gas line and the vent. A tank swap is a permit job in most places.
What a contractor will ask you
Have these ready and you skip the back-and-forth.
- When you first noticed the water. "More than a week ago" is a useful answer.
- How old the heater is. The build date is in the serial number on the label.
- Gas or electric.
- Where the water collects: right under the tank, or around the pipes and valves above it.
- Whether the water meter stops when you close the cold shutoff above the heater.
- Whether the T&P discharge pipe is wet or dripping.
- Whether the floor at the base or in the drain pan is wet or dry.
- A wide photo of the heater and the area around the leak.
Common questions
- Is a leaking water heater an emergency?
A slow drip is not, but it is on a clock. Close the cold shutoff above the heater if the water is spreading, and get it looked at within a few days. A sudden gush of water means shut the cold valve and the gas or breaker now.
- Can a leaking water heater be repaired instead of replaced?
Yes, when the water comes from a fitting, the T&P valve or the drain valve. Those parts sit outside the tank and get replaced in one visit. Water from the tank itself is the one leak nobody repairs.
- Why is the floor dry if the heater is leaking?
The water is evaporating off a warm tank before it reaches the floor, or it is running down the back and into a pan. That points to a slow leak high up, usually at a connector on top.
- My water heater is under 5 years old and leaking, is it under warranty?
Probably, on the tank. Most tanks carry a 6 year parts warranty, and the leak has to be confirmed as a tank failure. The warranty covers the unit and not the labour to fit it.
- How do I know if it is the water heater or a pipe near it?
Close the cold shutoff above the heater and watch the meter with all taps off. A meter that keeps creeping means the leak is upstream in the house pipe, not at the heater.