A water heater leak can spread across a garage, closet or utility room in minutes. Shut off the cold water supply to the tank, cut the power or gas, and stop the water from spreading. Everything else can wait until those three things are done.
This guide walks through those steps first. Then it explains how to tell a slow leak from a failed tank, what usually gets wet, what to photograph and when to bring in a professional.
Water Heater Leak: Do These Three Things First
Work in this order, because each step makes the next one safer. Tank water can be hot enough to scald, so keep your hands and feet out of standing water near the unit. If water is touching the electrical panel or you smell gas, leave the area and call 911 or your gas utility. Any water heater leak gets the same first response, whether it is a drip or a flood.
Shut off the cold water supply to the tank
Find the cold water inlet valve on the pipe entering the top of the tank. Turn a round handle clockwise until it stops. If it has a lever, turn it so it sits crosswise to the pipe. This stops fresh water from feeding the water heater leak. If the valve will not close, shut off the main water valve for the house instead.
Turn off the power or gas
Next, cut the heat source. For an electric unit, switch off its breaker at the panel. However, do not reach for the panel if you would have to stand in water to do it. For a gas unit, turn the gas control knob to the off position. A heating element or burner running on an emptying tank can fail, so this step matters even during a small water heater leak.
Stop the water from spreading
Then limit the damage. Lift rugs, boxes and furniture off wet floors. Soak up standing water with towels, a mop or a wet/dry vacuum plugged into a dry outlet. Water from a water heater leak wicks into drywall and flooring quickly, so move fast on anything absorbent. Also open doors and run fans to move air, but do not count on that to dry what is inside walls.
Slow Water Heater Leak or Failed Tank?
The source of the water tells you how serious the problem is. A slow water heater leak usually comes from a fitting, valve or connection. A failed tank means the steel tank itself has rusted through or cracked.
Signs of a slow leak:
- Drips or damp spots at the pipe connections on top of the unit
- Moisture around the drain valve near the bottom
- A small puddle that stops growing once the cold water valve is closed
Signs of a failed tank:
- Water coming from the base or the body of the tank, not a connection
- Rust-colored water or rust streaks running down the tank
- A large amount of water that appeared quickly and keeps coming until the tank empties
A failed tank cannot be repaired, but a loose fitting or worn valve sometimes can. Either way, have a plumber check the unit before you turn it back on. Water coming from the pressure relief valve or its discharge pipe also needs a plumber, because it can point to a pressure or temperature problem.
Where a Water Heater Leak Spreads
Water follows gravity and the easiest path, so the damage often reaches farther than the puddle suggests. Where a water heater leak ends up depends on where the unit sits.
- Garage: Water runs across the slab to the bottom of the walls and soaks stored boxes and anything on the floor.
- Closet or utility room: Water moves into baseboards, drywall and flooring, and it often runs under the wall into the next room.
- Basement: Water reaches carpet, finished walls and stored items.
- Attic: Water soaks insulation, then comes through the ceiling below as stains, bubbling paint or a sag.
If a ceiling is bulging, stay out from under it and avoid switching on lights or fans in that area. Drywall, insulation, carpet padding and particleboard cabinets absorb water quickly. Those materials are the most likely to need removal if they stay wet.
What to Photograph Before You Clean Up
Clear photos show what a water heater leak did before cleanup changes the scene. Take them after you shut everything off and before you move much. Also keep any wet items you plan to throw away until they are photographed.
- Wide shots of every affected room, floor to ceiling
- The water heater, its label (model and serial number) and the spot where it is leaking
- Water lines, stains or bubbling on walls, ceilings and flooring
- Damaged belongings, one item at a time
- A slow video walking through the area while you describe what you see
Write down when you found the leak and when you shut off the water. Then call your insurance company to ask how to report the loss and what they want to see. Only your insurer can tell you what your policy covers.
When a Water Heater Leak Needs a Restoration Company
A plumber fixes or replaces the heater. A restoration crew deals with the water it left behind. A water heater leak usually needs a professional once any of these apply:
- Water has reached carpet, padding or a second room
- Drywall, baseboards or insulation are wet
- A ceiling is stained, bubbling or sagging
- A tank failure released a large volume of water
- You cannot tell how far the water traveled
Water hidden behind walls and under floors stays wet even when the surface looks fine. The EPA’s mold guidance advises drying wet materials within 24 to 48 hours to help prevent mold growth.
Our crews use moisture mapping and thermal imaging to find hidden water, then set up structural drying equipment. You can read more on our water damage remediation page, or see what to expect in our water damage drying timeline. If you are worried about mold, our guide to mold after a leak covers the first 48 hours.
Our phone is answered 24/7, so you can contact us at any hour to talk through what you are seeing.
Water heater leak: common questions
Can I keep using hot water after a water heater leak?
No. Once you shut off the cold water supply to the tank, the heater has no water to heat, and running a unit with a water heater leak is not safe. Wait until a plumber has inspected it and repaired or replaced it.
Is a water heater leak an emergency?
Treat it as urgent if water is flowing from the tank, reaching the electrical panel or soaking walls and ceilings. A slow drip at a fitting is less urgent, but you should still shut off the water and have a plumber look at it soon.
Should I drain the tank after a water heater leak?
Shutting off the cold water, the power or gas, and the spread of water comes first. Draining the tank is usually a job for your plumber, especially because the water inside can be hot enough to scald.
How soon can mold grow after a water heater leak?
Mold can begin to grow when materials stay wet for 24 to 48 hours. That is why a water heater leak that soaked drywall, insulation or carpet padding should be dried quickly.
Who fixes the damage from a water heater leak, a plumber or a restoration company?
A plumber repairs or replaces the water heater itself. A restoration company removes the water, dries the structure and handles the damage the water heater leak left behind.