Water heater leaking — what to do right now
Where it's leaking from tells you almost everything. One location means replace it today; the others are usually a repair.
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Shut it down first
- Close the cold water supply valve at the top of the heater. Turn clockwise.
- Turn off the energy. Gas: set the control dial to “off” or “pilot.” Electric: switch off the breaker.
- Don't drain it yet unless it's actively flooding — a plumber may want to see it as-is.
- Move anything stored nearby and get water away from the base.
Find where it's coming from
| Location | What it means | Repair or replace |
|---|---|---|
| The tank body itself, or pooling from underneath | Internal corrosion has breached the tank | Replace. There is no repair for this |
| Fittings at the top (inlet/outlet) | A loose or corroded connection | Repair — often straightforward |
| The T&P relief valve | Excess pressure or temperature, or a failed valve | Repair — but investigate the cause |
| The drain valve at the bottom | A worn or unseated valve | Repair — inexpensive |
| Condensation on the tank | Not a leak at all — common in humid areas with cold incoming water | Nothing needed |
The temperature and pressure relief valve is the safety device that prevents a water heater from becoming an explosion hazard. If it's discharging, something is wrong — excessive pressure, excessive temperature, or a failed valve — and the correct response is to find out which. Plugging it is genuinely dangerous.
If the tank is leaking, act today
Tank failures are progressive and then sudden. A weep from the tank body means the internal lining has been breached and corrosion is working outward. There's no reliable way to predict how long you have between a weep and 40 to 80 gallons on the floor, which is why this is a same-day problem rather than a next-week one.
Replacement typically runs $1,200–$3,000 installed for a standard tank unit. Expect current-code items to be added — expansion tank, drip pan and drain, seismic strapping in some states, updated venting, permit and inspection. Those are legitimate, not upsells, but ask for them itemized.
Preventing the next one
- Flush the tank annually. Sediment insulates the bottom, makes the burner or element work harder, and shortens life. Almost nobody does this and it genuinely matters.
- Check the anode rod every few years. It's a sacrificial component that corrodes so the tank doesn't. Replacing a $40 rod can add years.
- Test the T&P valve annually. Lift the lever briefly and confirm it discharges and reseats.
- Fit a drip pan with a drain if the heater sits above living space. Cheap, and it converts a catastrophe into a nuisance.
- Consider a leak alarm. About $15 and it wakes you up.
Frequently asked questions
Is a leaking water heater dangerous?
A tank leak is primarily a flooding risk — 40 to 80 gallons. A gas unit leaking near burner components, or a T&P valve discharging, warrants prompt attention for safety reasons too. Shut off water and energy to the unit.
Can a leaking water heater be repaired?
If the leak is at a fitting, valve, or the drain, usually yes. If it's from the tank body, no — that's replacement. Anyone offering to repair a leaking tank body is someone to walk away from.
How long can I leave a leaking water heater?
If it's the tank body, don't. Failures accelerate unpredictably. Shut off the supply and arrange replacement the same day.
Why is water pooling under my water heater?
Most likely the tank has corroded through, though it can also be condensation, a leaking drain valve, or T&P discharge running down the side. Dry the area completely and watch where water reappears — that tells you which.
Plumbing emergency right now?
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