Water heater leaks: the signs before it fails
A tank water heater holds a few dozen gallons and works under pressure all day. When it fails, the water goes onto the floor in minutes. The good news is that most tanks give notice. The bad news is that notice looks like small things: a rumble, a rusty tint, a damp patch. Here is what those small things mean.
How a tank fails
Inside a steel tank, a glass lining keeps the water away from the metal. Over time the lining cracks in places, and a metal rod called an anode, there to corrode in place of the tank, wears down. Minerals in the water settle to the bottom as sediment, which makes the burner or element work harder and can overheat the bottom of the tank. Eventually the steel corrodes through, usually at a seam or the base. At that point the tank is done, and no repair fixes it.
Signs by stage
| What you notice | What it may mean | What to do |
|---|---|---|
| A rumbling, popping or knocking when it heats | Sediment built up at the bottom of the tank | Ask a plumber about flushing it. Follow the manufacturer's instructions. |
| Hot water that looks rusty or smells metallic | Corrosion inside the tank, or an anode rod that is spent | Have it looked at soon. Replacement may be near. |
| Hot water runs out faster than it used to | Sediment or a failing element | Service it, or plan for a replacement. |
| Moisture or rust at the base, fittings or seams | A fitting is leaking, or the tank itself is starting to | Dry the area and check again the next day. If it returns, call a plumber. |
| Water dripping from the relief valve discharge pipe | Pressure or temperature issue, or a worn valve | Call a plumber. Do not plug the pipe. |
| A puddle under the tank | A fitting or the tank has failed | Shut it down and call a plumber, and us if it has spread. |
Age is the quickest clue
Look at the label on the side of the tank. The serial number or a date code often shows the month and year of manufacture. Tanks do not last forever. A tank past its first decade deserves a yearly look, and one that is rusting at the base or seams is past saving. If yours is old and you are planning a trip, a replacement before it fails costs less than a flood.
In older neighborhoods the tank in the basement may be a second or third one, installed years ago and not looked at since. In older neighborhoods, like the one described on our Maryland City page, an original or early replacement tank may still be in service, so checking the date is worth five minutes.
Water heater leaking now?
Close the cold inlet and cut the power or gas, then call. We start on the water.
Call (301) 786-0888Gas, electric and tankless
A gas tank has a burner, a gas line and a flue, and any leak calls for shutting off the gas supply and the water inlet. An electric tank has heating elements and a power feed, so the breaker comes off before anyone touches it in standing water. Both leak the same way, from the tank or the fittings. A tankless unit has no big tank to fail, but it has fittings and a heat exchanger that can leak, and in hard water it can scale up. Whatever the type, the water on the floor is the same problem, and the first step is always to stop the supply.
The yearly check
- Read the date code on the label.
- Look around the base, the fittings and the pipes with a flashlight.
- Look at the relief valve and its discharge pipe for drips or mineral stains.
- Touch the floor under the tank. It should be dry.
- Listen when it heats for rumbling or popping.
- Check that the pan under the tank, if there is one, is dry and that its drain line is clear.
If the tank sits above finished space, such as an upstairs closet or an attic, a drain pan with a drain line and a leak sensor are worth adding.
What to do when it starts leaking
- Close the cold water inlet valve on top of the tank.
- Turn off the power at the breaker for an electric unit, or set a gas unit's control to off or pilot. Do not touch wiring in standing water.
- Open a hot tap somewhere in the house to relieve pressure and let the tank drain.
- Attach a hose to the drain valve at the base, if you can reach it, and run it to a floor drain or outside.
- Photograph the damage and the tank label.
- Call a plumber about the tank, and a water extraction crew about the floor.
Cleaning up after the tank
Water from a tank is clean when it leaves the tank, so it starts as Category 1, and the first priority is to get it out of the house before it picks up dirt or reaches finished materials. Pumps and extractors handle the standing water, wet drywall and insulation near the base are removed if they have soaked, and the area is dried with dehumidifiers and air movers. The steps are under appliance and water heater leak cleanup. Emergency water extraction is where the first visit begins, and water damage restoration carries the rest.
After a tank fails
- Appliance & Water Heater Leak Cleanup Cleanup after a tank or appliance leak.
- Emergency Water Extraction Pumping standing water first.
- Water Damage Restoration The whole process from source to dry.
Local note: see our page for Maryland City. It covers the age of the housing there.