The Water Heater Is Leaking!

Photo: Josh Larios/FlickrA leak from an appliance that holds upwards of 30 gallons of scalding-hot water is never a reassuring sight. But stay calm. The important thing is not so much that there's leakage but where the leakage is coming from. Some problems can be repaired by a handy homeowner, and some require a pro. Others call for all-out replacement of the appliance (ASAP most likely).

Of course, when you find a water heater leaking, or at least water in the area, the primary concern is making sure it doesn't get worse. Let's look at the main areas to check for a quick diagnosis.

Water Supply Piping

A standard tank-style water heater has two water pipes running into its top end: one is the cold water supply coming into the tank; the other is for the hot water leaving the tank. You can easily identify them by feel, and the cold line typically has a shutoff valve somewhere near the tank. Check all visible connections on both water lines. If there's slow leakage at any threaded fittings, try tightening the fitting's nut with an adjustable wrench. If one of the supply pipes or hoses has sprung a leak (hopefully after the shutoff valve), close the valve on the cold-water line to stop the flow of pressurized water. If a pipe or fitting is leaking before the valve (opposite the water heater), you'll have to shut off the water to the whole house at the main shutoff valve.

Tank Valves

A water heater that's leaking may have a problem with one of two valves mounted on the side and/or top of the tank.

The drain valve is near the bottom of the tank and may look like an outdoor hose bibb or a just an open-ended plastic pipe with a knurled or notched ring at its base. If you see leakage at the valve, try closing the valve tighter, and if that doesn't work, replace the valve. You can do this yourself after draining the tank (we won't go into details here, but it's a straightforward process that's covered by numerous reputable sources online and in home improvement books).

The other valve is the TPR (temperature and pressure release) valve, located at the top of the tank or in the sidewall near the top. It has a little metal tab or lever on its body and is connected to a pipe that typically runs straight down along the side of the tank, stopping about 6 inches above the floor. The pipe may also direct to a floor drain or run through the floor, if the water heater is on a first floor above a crawl space or basement. The TPR valve's job is to release water should the temperature or pressure inside the tank get too high. If the valve activates, it will discharge a forceful spray of water through the discharge pipe (after this occurs, shut off the heater's power or gas and water supplies and call a plumber). The results of a full-on TPR activation look different from a drip, which indicates the valve is bad and needs to be replaced; call a plumber for this, too.

Tank Leakage

Water heater tanks are made of steel, and water corrodes steel. If this sounds like planned obsolescence, it is; water heaters aren't designed to last forever. To stave off corrosion, standard tanks have a glass lining and a magnesium anode rod that attracts corrosive elements in the water, sort of like how a no-pest strip attracts flies (the rod should be checked periodically and replaced as needed). But the tank can rust eventually and possibly rupture like the hull of the Titanic. If you discover your water heater leaking from the tank itself, it's time for a new tank. Shut off the power/gas and cold water supply and drain the tank, then contact a plumber.

However, a couple of things may trick you into thinking the tank is shot: Electric water heaters can leak where the heating elements (most full-size heaters have two) mount to the sidewall of the tank, in which case you probably need a new gasket instead of a new tank. Replacing a gasket or element is doable for intrepid homeowners; just make sure to follow the process carefully -- from shutting off the power to purging and refilling the tank at the end of the job. The other thing to check for is condensation. Water heater tanks can become covered with condensate upon first filling up and sometimes in cold weather. Condensation is widespread and more like sweating than leaking. You should be able to tell the difference by keeping close tabs on the unit.

Repair or Replace?

Water heaters aren't terribly expensive to buy and have professionally installed. They also have a limited service life that should be respected. An old water heater leaking could mean thousands of dollars in water damage. Keep this in mind if you're faced with an expensive repair on your existing heater. Given its job and the fact that it holds a huge quantity of water in or near your living or storage space, it's not a good idea to exceed the service life by too much. Most standard units are good candidates for replacement after about 10 years.

Philip Schmidt writes for

Updated October 23, 2018.

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