Cut the heat first: on gas, turn the control knob to OFF and close the gas valve; on electric, switch off its breaker. Then close the cold water valve on the pipe above the heater. Never touch a breaker while standing in water; if the panel isn't safe to reach, close the water and call the utility.
How do you turn off a gas water heater that's leaking?
Turn the gas control off, then close the gas supply valve. A.O. Smith's draining steps start the same way:
- 1Turn the gas control/temperature knob to the "OFF" position.
- 2Turn "OFF" the gas supply at the manual gas shut-off valve on the gas line near the heater. Its handle is usually a lever. Turn it so it sits across the pipe.
- 3Close the cold water inlet valve.
The manual is direct about one emergency case: "Should overheating occur or the gas supply fail to shut off, turn 'OFF' the manual gas shut-off valve to the appliance."
### What if you smell gas?
Then it's no longer a water leak. It's a gas emergency, and the steps change. Southwest Gas says to "Exit the area or building immediately," not to operate "any electric switches, thermostats, or appliance controls," and "From a safe place, call 911 and Southwest Gas at 877-860-6020, day or night." Leave the water for later. Our page on what to do when the house smells like gas covers it.
How do you turn off an electric water heater that's leaking?
Switch off its breaker at the electrical panel. The water heater usually has its own breaker, often labeled on the panel door. Rheem's electric water heater manual says owners should know "the location of the circuit breaker and how to shut it off if necessary," and to "Turn off the circuit breaker if the water heater has been subjected to overheating, fire, flood, physical damage."
Do this before draining. Rheem's manual says "Shut off power to the water heater before draining water," and warns: "DO NOT turn on water heater unless it is filled with water." Rheem's control even has an error code for "Dry Fire (Heating without water)."
### What if the floor is already wet?
Stay out of the water if it's near outlets, cords, or the panel. Safe Electricity warns: "Never attempt to turn off power at the breaker box if you must stand in water to do so. If you can't reach your breaker box safely, call your electric utility to shut off power at the meter." It also says never to touch "electric wires, switches, or fuses when you're wet or when you're standing in water."
If the panel is dry and you can reach it from a dry spot, turn off the breaker. If not, call the utility.
How do you stop the water going into a leaking water heater?
Once the heat is off, close the cold water inlet valve. It sits on the cold water pipe coming into the top of the heater, usually within a few feet of the tank. A.O. Smith's manual tells installers to put "a shut-off valve in the cold water inlet line" that is "close to the water heater and be easily accessible," and tells owners to "Know the location of this valve and how to shut off the water to the heater."
The valve is one of two types:
- A lever handle (ball valve). Turn it a quarter turn so the handle sits across the pipe, not along it.
- A round wheel handle (gate valve). Turn it clockwise until it stops. Older gate valves can be stiff or leak at the stem. Don't force one hard enough to break it.
Closing this valve stops the supply. It doesn't empty the tank, so a leaking tank will keep dripping until the water inside drains out or the level drops below the leak.
If the cold water valve won't close, or the leak is from the pipes or valve itself, shut off the main water valve for the house. In most Phoenix-area homes it's near where the water line enters, often on an outside wall or in the garage. Our page on how to shut off water to a fixture covers finding shutoff valves. If you can't shut the water off at all, the City of Phoenix lists an emergency line, 602-261-8000, for "an emergency and requires field staff to turn off your water due to a leak."
Should you drain the water heater after shutting it off?
Only if the leak is from the tank and water is still coming out. Draining empties the tank so the leak stops sooner. Rheem's manual gives the steps for an electric model, and A.O. Smith's are the same for gas once the gas is off:
- 1Make sure the power or gas is off, and the cold water valve is closed.
- 2Open a hot water faucet somewhere in the house to let air into the tank.
- 3Attach a garden hose to the drain valve at the bottom of the heater and run it to a floor drain, outside, or a spot lower than the tank.
- 4Open the drain valve.
The water will be hot. Rheem warns that drained water "may be hot enough to present a scald hazard and should be directed to a suitable drain to prevent injury or damage." Give the tank time to cool if you can.
Is a leaking water heater an emergency?
It depends on where the water is coming from and where it's going. Use this to decide:
| What you see | How urgent | Next step |
|---|---|---|
| Water spreading onto finished floors, carpet, or drywall | Urgent | Shut off water and heat now, then call a plumber |
| Steady drip from the tank bottom | Soon | Shut off, drain, plan a replacement |
| Water from the relief valve pipe | Soon | Shut off and call; A.O. Smith says if the valve "continues to release water, immediately close the cold water inlet" and replace the valve |
| A small drip at a fitting on top | Can often wait | Close the cold valve, dry it, and watch it |
| Gas smell anywhere | Emergency | Leave, then call 911 and the gas company |
Never cap or plug a dripping relief valve pipe to stop the leak. A.O. Smith's manual says the discharge pipe "Shall not be plugged or blocked." The valve is a safety device. See why a water heater relief valve leaks.
Dry what got wet. The EPA says "If wet or damp materials or areas are dried 24-48 hours after a leak or spill happens, in most cases mold will not grow." A heater that has sat in water needs a professional look before it runs again. A.O. Smith's manual says not to use the appliance "if any part has been under water," and to have a qualified installer "replace a flooded water heater. Do not attempt to repair the unit! It must be replaced!"
For the causes of a leak and whether it can be repaired, see why a water heater leaks from the bottom and whether to repair or replace a water heater.
HQ Plumbing & Air answers water heater leaks 24/7 across the Phoenix area, licensed and insured, with upfront pricing. See our water heater service.
Heat off, water off, then call. That order keeps a leak from becoming a flood or a burned-out heater.