Water Heater Burst: What to Do Right Now
On this page (6 sections)
The Short Answer: Stop the water first: close the cold-water inlet valve above the heater, or the main house shutoff if you can’t reach it safely. Then shut off the energy from a dry place: the water heater’s breaker for electric, the gas control to OFF for gas. Keep people and pets away from hot water and from anything electrical near the water. Then call a plumber.
First 10 minutes
- Close the cold-water inlet. It is the valve on the pipe entering the top of the heater, usually marked cold. A lever handle is closed when it is across the pipe. A round handle turns clockwise. If you can’t find it or can’t reach it safely, close the main water shutoff for the house.
- Shut off the energy. Electric: switch off the double-pole breaker for the water heater. Gas: turn the control knob to OFF. If you also want to close the gas supply valve, the handle goes across the pipe. If you smell gas, leave and call from outside instead.
- Keep hot taps closed. Opening a hot faucet lets air into the tank, and the tank then drains faster through the leak.
- Protect the house. Move belongings, start removing water with towels or a wet vacuum, and take photos for insurance.
- Leave the relief valve alone. Never plug or cap the T&P valve or its pipe, even if it is discharging.
If you live in an apartment or can’t identify the valves, how to turn off the water heater in an apartment shows where they usually are.
Did the tank burst, or is something else flooding?
| What you see | What it likely is | What it means |
|---|---|---|
| Water pouring from the jacket or a split at the bottom | Tank failure | Heater must be replaced |
| Steady stream from the relief valve pipe | Relief valve opening on pressure or temperature, or stuck open | The tank may be fine; the cause must be found |
| Water spraying from a fitting or connector on top | Failed connector or nipple | Repairable |
| Slow puddle that grew over days | Drain valve, fitting, or early tank leak | See water leaking from the bottom of the tank |
| Loud bang at the burner, no water | Delayed ignition, not a burst | See water heater made a loud bang |
A relief valve that is discharging hard means the tank’s pressure or temperature is too high, or the valve has failed. Either way, it needs a plumber. If the relief valve was involved, see pressure relief valve stuck open.
Can you still use water?
Once the water heater’s cold inlet is closed, the rest of the house usually still has cold water. Toilets and cold taps work, though some single-handle faucets may mix poorly. If you had to close the main shutoff, you’ll have no water until the heater is isolated. Can you still use water if the water heater is leaking? has more detail.
What the plumber will do
The plumber confirms where the water came from. If the tank has failed, they drain and remove it and install a replacement that meets current code: a properly piped relief valve discharge, a drain pan where required, and thermal expansion control where the water system is closed. If the relief valve discharged, they check house water pressure, the expansion tank, and the thermostat, because a stuck thermostat or very high pressure can cause the valve to open.
A failed tank can’t be repaired. Patches and sealants are not safe on a pressurized tank.
Why tanks fail
Most tank ruptures come from corrosion after years of service, usually at the bottom. They happen faster with hard water, an anode rod that has worn out, or high water pressure. A capped or blocked relief valve combined with a thermostat failure is a rare but dangerous cause. That is why relief valves must never be blocked. Knowing the age of your water heater helps you plan replacement before a failure.
Frequently Asked Questions
Q: Is my insurance likely to cover water heater flood damage? A: It depends on your policy. Sudden water damage is often treated differently from long-term leaks. Take photos and video before cleanup, keep damaged items if you can, and contact your insurer promptly.
Q: Should I drain the rest of the tank? A: Not usually. Once the inlet is closed, the flow slows to whatever is left in the tank. Leave the draining to the plumber, especially if the water is still hot or the heater is electric.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- A. O. Smith technical bulletin 51: puddles around a heater (opens in a new tab)Common water-leak sources and the distinction between fittings and a failed tank.
- A. O. Smith technical bulletin 45: thermal expansion (opens in a new tab)Background on pressure rise in a closed water system. Pressure testing and repairs are professional work.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
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