Water Heater Leaking? What to Do Right Now and What the Leak Location Tells You

First five minutes

Before you figure out why it is leaking, limit the damage. On top of the water heater is a cold-water inlet pipe with a shutoff valve, usually a round gate valve or a quarter-turn ball valve. Close it. That stops new water from entering the tank, so whatever leaks out from here on is limited to the 40 or 50 gallons already inside.

Then take the heat source off. On a gas unit, turn the dial on the gas control valve at the front of the tank to Off; do not touch the gas supply pipe or the union. On an electric unit, switch off the two-pole breaker in the panel. A tank that drains while the burner or elements are still on can overheat, and on an electric heater a dry element burns out in seconds.

If the water is spreading toward the furnace, a finished floor, or stored belongings, get towels or a wet vac on it and move what you can. If the leak is significant, attach a garden hose to the drain valve at the bottom of the tank, run it to a floor drain or the sump pit, and open the valve to drain the tank down. Open a hot water faucet upstairs to let air in so it drains faster.

If at any point you smell gas, stop, leave the house, and call DTE at 800-947-5000 and 911 from outside.

Finding the leak

Water travels. A drip from a fitting on top runs down the jacket and pools at the base, which makes every leak look like a tank failure at first glance. Dry the floor and the outside of the tank, then watch where the water reappears. A flashlight and a paper towel pressed against each suspect spot narrows it down fast.

• Top of the tank, at the hot or cold pipe connections. The dielectric nipples or the flex connectors corrode, especially with the hard water across Washtenaw County, and a threaded joint weeps. Repairable, often a quick one.
• Side of the tank, at the TPR valve. The temperature and pressure relief valve has a discharge pipe running down toward the floor. If water is coming out of that pipe, the valve is doing its job or has failed. More below.
• Bottom, at the drain valve. The plastic drain valves on many tanks crack or do not reseat after a flush. Repairable with a brass replacement.
• Bottom, from under the jacket, with no fitting nearby. The glass lining inside the steel tank has cracked, water reached the steel, and the tank has rusted through. Not repairable.
• Around the burner access door or at the base on a gas unit. Could be the tank, or could be condensation; see below.

When it is the TPR valve

The temperature and pressure relief valve opens if the tank exceeds 150 psi or 210 degrees, which is a safety release, not a leak. If the discharge pipe drips a little after the burner runs, the likely causes are high pressure in the house from thermal expansion with no expansion tank, especially in homes with a pressure-reducing valve or a backflow preventer on the main; a thermostat set too high; or a TPR valve that has mineral deposits on its seat and will not close fully.

A constantly dripping TPR valve should be replaced, and if the cause is thermal expansion, an expansion tank gets added at the same time. Most Ypsilanti and Ann Arbor municipal water customers with a newer meter setup have a check valve on the main, which makes the expansion tank necessary, and inspectors here look for one on a new installation. Do not cap the discharge pipe or plug the valve. Ever. A water heater with a disabled relief valve is a pressure vessel with no release.

When it is condensation, not a leak

A gas water heater that has just been refilled, or that is working hard on a cold morning when the incoming water is near 40 degrees, condenses water vapor on the cold tank and in the flue. That condensation drips onto the burner and the floor and can look exactly like a leaking tank. The giveaway is that it stops once the tank comes up to temperature and does not come back. If the puddle is small, appears only after a heavy hot-water draw, and dries up within an hour, give it a day before you decide the tank is done. If it keeps coming, it is not condensation.

When the tank has failed

A tank leak from the bottom of the jacket is terminal. The steel tank is lined with a thin glass coating, protected by an anode rod that sacrifices itself to corrosion instead of the steel. When the anode is consumed, which in Washtenaw County's 8-to-12-grain municipal water and the much harder well water out in Augusta, York and Salem Township takes about five to eight years, the steel starts rusting. Once it rusts through, there is no patch, no sealant, and no repair. The leak will get worse, and a bottom seam that has let go can turn into a basement flood in an afternoon.

At that point the questions are how old the unit is and what to replace it with. Most tanks in our area fail between 8 and 14 years, and if yours is in that range the replacement is overdue rather than premature. Our water heater installation visits include hauling out the old tank, a new TPR valve and discharge pipe, an expansion tank where needed, and the mechanical permit and inspection. We also look at the flue, because a tank replaced after a furnace was converted to high-efficiency often needs a chimney liner to draft safely.

Repairs that do make sense

A tank with years left in it should not be replaced over a fitting. A weeping dielectric nipple, a cracked drain valve, a failed TPR valve, a leaking gas control valve union, a corroded flex connector: all of these are quick repairs we do on the first visit. If the tank is under 8 years old and the leak is anywhere other than the tank body, it is worth a water heater repair call before anyone talks replacement.

While we are there, we check the anode rod. A rod that is mostly consumed can be replaced, which on a mid-life tank buys several more years before the steel is exposed. Our water heater maintenance guide explains the flush-and-anode routine that keeps a tank from failing early in hard water.

Preventing the flood next time

Most water heaters in Southeast Michigan sit on the basement floor near the furnace, a few feet from the sump pit, and when they fail the water finds the low spot. A drain pan under the unit piped to a floor drain, which is required for installations where a leak could damage finished space, contains a slow leak. A leak alarm, a battery puck that sits in the pan or on the floor and screams when it gets wet, costs very little and is the reason some of our customers caught a leak on day one instead of week two. An automatic shutoff valve that closes the supply when the alarm trips is the next step up and is worth it for a finished basement.

And know the age. The serial number on the data plate encodes the manufacture date. A tank past 10 years with any sign of rust at the fittings or weeping at the base is a tank to replace on your schedule rather than on its own. The lifespan and replacement signs guide covers what to watch for.