Symptoms
- Water pooling under or around the tank
- Rust-colored water near the base
- Leak persists even with all fittings dry
- Tank is older, often 8–12+ years
Likely causes
- CommonInternal tank corrosion has created a hole in the steel linerOnce the glass lining and anode rod protection are exhausted, the steel tank rusts through.
- CommonFailed drain valve at the bottomA leaking drain valve can look like the tank itself is leaking.
- PossibleLoose or failed bottom fittingA fitting near the bottom, distinct from the tank shell, can be the real source.
What to do
- Turn off power (electric) or set the gas valve to 'pilot'/off, and shut off the cold water supply valve to the tank.
- Dry the area around the base and drain valve completely with towels.
- Watch closely for a few minutes to see if water is coming from the drain valve specifically versus the tank seam or shell.
- If it's the drain valve, that alone can sometimes be replaced without replacing the whole tank.
- If water is seeping from the tank shell itself or from underneath with no clear fitting source, treat it as tank failure.
- Place a pan and towels under the leak and plan for replacement promptly, since a failing tank can worsen quickly.
Tools and parts
- Towels
- Flashlight
- Adjustable wrench
Water heater drain valveSearch: “water heater drain valve replacement”
Replacement water heater tankSearch: “40 gallon gas water heater replacement”
When to call a pro
A leak from the tank shell itself means the tank has failed and needs full replacement; call a plumber promptly to avoid water damage.
Safety
Use caution
Shut off both the water supply and the power or gas to the unit before inspecting a leak closely.