Water Heater Leak or Failure, Shutoff and Cleanup

Shut It Down Safely

Start by stopping new water from entering the tank and stopping the heat.

1. Close the cold water inlet valve. It is on the pipe that goes into the top of the tank, usually on the cold side marked with blue or a C. Turn a round handle clockwise, or turn a lever a quarter turn so it sits across the pipe.
2. For a gas heater, turn the control knob on the gas valve to OFF. Most units also have a gas shutoff on the supply line. Turn that handle so it sits across the pipe.
3. For an electric heater, switch off its breaker at the panel. It is usually a double breaker, often labeled water heater.

If the cold inlet valve will not close or is leaking itself, shut off the main water valve to the house.

If water is pooling near the breaker panel, outlets or the heater’s electrical connections, do not stand in it to reach anything. Shut off power from a dry spot, or call an electrician.

If you smell gas at any point, leave the house and call your gas utility from outside. Do not flip switches or light anything.

Find Where the Water Is Coming From

The source decides whether this is a quick repair or a new heater. Dry the area with towels, then look closely with a flashlight.

Leaks at the top can run down the outside of the tank under the jacket and show up at the bottom, so do not jump to conclusions. Check the top first. A tank that is leaking from inside, through the steel, cannot be patched. Plan on a replacement.

When the Relief Valve Is Dripping

The temperature and pressure relief valve is the brass valve on the top or side of the tank with a pipe running down toward the floor. It opens to let water out if the tank gets too hot or the pressure gets too high. Most are set to open at about 150 psi or 210°F. It is the part that keeps a tank from exploding.

A valve that drips or discharges is doing its job, or it is worn out. Either way, never cap the discharge pipe, plug the valve or remove it.

Common reasons it opens.

• High house water pressure. Screw a pressure gauge onto a hose faucet. Plumbing codes generally require a pressure reducing valve when street pressure is over 80 psi. Many homes run best around 50 to 70 psi.
• Thermal expansion. Heated water expands. If your home has a check valve or pressure reducer, the extra volume has nowhere to go. An expansion tank on the cold line fixes this.
• Thermostat set too high or a failed thermostat.
• Worn valve. Debris or age keeps it from sealing.

Any relief valve problem is a job for a plumber, who can test the pressure, replace the valve and add an expansion tank if needed.

How to Drain the Tank

You need to drain the tank if it is leaking from the tank body, or if a plumber asks you to before replacement. A standard tank holds 40 to 50 gallons, which weighs about 330 to 420 pounds, so draining also makes it safe to move.

1. Make sure the gas is off or the breaker is off, and the cold inlet valve is closed.
2. Let the water cool for a few hours if you can. Tank water is hot enough to scald.
3. Attach a garden hose to the drain valve near the bottom. Run it to a floor drain or outdoors to a spot lower than the valve.
4. Open a hot water faucet somewhere in the house. This lets air in so the tank drains.
5. Open the drain valve slowly with a screwdriver or the handle.

Sediment can clog the drain valve, especially in areas with hard water. If flow slows to a trickle, briefly open the cold inlet valve to stir the sediment, then close it again.

Plastic drain valves on older tanks can crack when turned. Turn gently. If it breaks, you will have a stream of hot water you cannot stop until the tank is empty, so have the hose connected first.

Cleaning Up the Water

Water from a water heater tank is usually treated as clean water, since it came from your supply. It may carry rust and sediment that can stain, so clean it up quickly.

• Vacuum standing water with a wet/dry vacuum and mop the rest.
• If the heater is in a closet or garage with drywall, check the walls with a moisture meter. Water wicks up drywall from the floor.
• If the closet has carpet next to it, pull the carpet back and check the pad.
• Remove baseboards along wet walls so air can reach them.
• Run a dehumidifier and a fan in the space for a few days.

A heater in an attic is a different story. A tank that fails in an attic can soak insulation and come through the ceiling below. Stay out from under a sagging ceiling and see the ceiling leak guide.

A water heater in a living space should sit in a drain pan piped to a drain or outdoors, and many codes require that. If yours has no pan, add one when the heater is replaced. A battery water leak alarm on the floor next to the tank, often $15 to $30, gives early warning.

Repair or Replace

Most tank water heaters last about 8 to 12 years, and less in areas with very hard water. Check the manufacture date on the label on the tank. It is often part of the serial number, and the manufacturer can decode it if it is not obvious.

Repair makes sense when the leak is at a fitting, a flex connector, the drain valve or the relief valve, and the tank itself is not leaking. A plumber can replace these parts in an hour or two.

Replace when the tank body is leaking, the bottom is rusted, or the heater is past about 10 years and has had repeated problems. Rusty water from the hot taps only can be an early sign the tank is corroding inside.

Replacing a water heater involves the gas line or a 240 volt circuit, venting for fumes and a new relief valve discharge. In most cities it needs a permit and inspection. A poorly vented gas heater can put carbon monoxide into the home. This is a job for a licensed plumber.

Tankless heaters rarely leak in large amounts, but they can drip from fittings or the relief valve. Turn off the water valves under the unit and the power or gas, and call a plumber.

Gas Water Heaters and Flood Water

If a gas water heater sat in water from a flood or a large leak, treat it as unsafe. Water can damage the gas control valve, the burner and the pilot assembly in ways you cannot see. Appliance makers and safety agencies advise that any gas control that has been under water should be replaced, not dried and relit.

• Leave the gas off at the heater’s shutoff valve.
• Do not try to relight the pilot.
• Have a licensed plumber or gas technician inspect the heater and its venting.

Check the vent too. A vent pipe knocked loose during cleanup can spill carbon monoxide into the house. Make sure you have working carbon monoxide alarms on each level, especially near bedrooms.

Electric heaters that sat in water also need to be checked by a professional before power is restored, since wet wiring and elements can short or shock.

If the heater is old and got soaked, replacement is usually the better choice than repair.

Step by Step

1. Close the Cold Inlet Valve

   Shut the valve on the cold pipe going into the top of the tank. If it will not close, shut the main water valve to the house.

2. Turn Off Gas or Power

   Turn a gas control to OFF and close the gas supply valve, or switch off the water heater breaker for an electric unit.

3. Find the Leak

   Dry the tank and floor, then check the top fittings, the relief valve, the drain valve and the bottom of the tank with a flashlight.

4. Check Water Pressure

   If the relief valve is dripping, screw a pressure gauge onto a hose faucet. Over 80 psi points to a pressure problem a plumber should fix.

5. Drain If the Tank Is Leaking

   Let the water cool, attach a hose to the drain valve, open a hot faucet in the house, and open the drain valve slowly.

6. Clean Up and Dry

   Vacuum water, pull back nearby carpet, remove baseboards and check drywall with a meter. Run a dehumidifier for a few days.

7. Document

   Photograph the leak source, the label with the date and the water damage before repairs. Call your insurer if nearby materials were damaged.

8. Call a Plumber

   Have a licensed plumber repair the fitting or valve, or replace the heater with a permit if the tank has failed.

Mistakes That Make It Worse

• Capping or plugging a dripping relief valve. It removes the safety that keeps the tank from bursting.
• Draining the tank with the power still on. Electric elements can burn out in seconds once exposed.
• Draining scalding water into a plastic tub or onto your feet. Let it cool and use a hose to a drain.
• Relighting a gas heater that sat in water. Damaged controls can leak gas or fail to shut off.
• Assuming a puddle means the tank failed. Leaks from top fittings often run down and look like a tank leak.

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