Can a water heater leaking from the tank be repaired?
Replace the water heater
No. Once the steel tank has corroded through from the inside, it cannot be sealed, patched, welded, or treated. The tank is glass-lined steel under constant pressure, and any patch fails against that. The unit has to be replaced.
A tank that is seeping can fail properly without much warning. Do not leave it running unattended, and keep the area around it clear.
How to tell it's this
- Water seeps from under the tank body with every fitting above it dry.
- It leaks constantly, whether the heater is running or not.
- Rusty or discoloured water, or rust staining on the base skirt.
- The unit is past about 8 years — storage tanks last roughly 8–12.
What to do
- Rule out the three cheap causes first: the drain valve, the T&P discharge pipe, and the connections at the top. People are sold replacements for all three.
- If it really is the tank body, shut off the cold water and cut the gas or power, and get quotes rather than waiting.
- Check the manufacture date in the serial number on the label. A tank inside its 6–12 year warranty may be replaced free, though the labour rarely is.
- Get two or three local estimates. Labour is 30–50% of the installed cost, so it is the number that varies most.
What it costs
Installed replacement in 2026: roughly $700–$1,800 for an electric tank, $1,000–$3,000 for a gas tank, and $1,200–$4,500 for tankless. These are typical ranges, not quotes.
Typical US ranges for 2026, not quotes. Labour is 30–50% of an installed price, so where you live moves these numbers more than anything else does. Get two or three local estimates.
If that's not it
The heater was fitted within the last year
A new heater leaking underneath →
You have not checked the spigot near the floor yet
The drain valve →
Not sure which of these it is?
Answer four questions — where it's leaking, tank or tankless, gas or electric, and how
old it is — for a specific cause, a repair-or-replace call, and a cost.