Emergency

Water Heater Leaking? What to Do Before the Plumber Arrives

Updated Jul 2026 · 5 min read

Photo by aamir dukanwala on Pexels

A leak is a warning, so act on it quickly

A puddle under the water heater rarely fixes itself. Sometimes it starts as a few drops around a fitting; other times you walk into a flooded utility closet. Either way, the goal in the first few minutes is the same: stop the water, cut the energy, and limit the damage while you line up a professional. Here is a calm order of operations you can follow.

Find where the water is coming from

Before touching anything, look at the tank. Water pooling near the top often points to a loose or failing connection at the cold inlet or hot outlet, or at the temperature and pressure relief valve. Those are sometimes fixable. Water seeping from the bottom of the tank usually means the inner steel shell has rusted through, and a corroded tank cannot be patched. Check the relief valve too: if it is discharging down its drain pipe, the tank may be overheating or overpressurized, which is a safety issue rather than a simple drip.

Lay a dry paper towel around each fitting and the base. It helps you tell an active leak from old condensation or a one-time spill.

Cut the power or gas first

Water and live electricity are a dangerous mix, so shut off the energy source before you start draining anything.

For an electric water heater, switch off its dedicated breaker in your main panel. Do not rely on a wall switch.

For a gas unit, turn the gas control dial to "Off," and if you are comfortable doing so, close the gas shutoff valve on the supply line running to the heater. Turning the dial to "Pilot" is not enough when the tank is leaking.

If you ever smell gas, do not flip switches or light anything. Leave the home and call your gas utility's emergency line from outside.

Shut off the water supply

Find the cold water shutoff valve at the top of the heater, on the incoming line, and close it. A round handle turns clockwise; a lever handle turns a quarter turn so it sits crosswise to the pipe.

If that valve is stuck or you cannot find it, shut off the main water supply to the whole house. That valve is usually where the water line enters the home, near the meter, or in a basement or garage wall. Closing it stops the flow feeding the leak even if the local valve fails.

Drain the tank when the leak is serious

A slow drip can often wait for the plumber with a bucket and towels underneath. A steady leak or a split tank is different, and draining it protects your floors and walls.

Attach a garden hose to the drain valve near the bottom of the tank and run the other end to a floor drain, a sump, or outside to lower ground. Open a hot water tap somewhere in the house to let air in so the tank drains smoothly. Then open the drain valve. The water leaving the tank may still be hot, so keep hands and pets clear of the outlet.

Draining a full tank takes a while, and that is fine. You are buying time and preventing a bigger mess, not racing a clock.

Contain the damage while you wait

Move boxes, laundry, and anything else off the floor around the heater. Water wicks into cardboard and drywall fast. Sop up standing water with towels or a wet vac, and get air moving with a fan so moisture does not settle into the subfloor. If the heater sits in a finished space, pull back rugs and lift furniture legs onto blocks.

Damp building materials that stay wet can grow mold, so drying the area thoroughly matters as much as stopping the leak. If water reached a wall cavity or a floor below, mention that when you call, because it may need attention beyond the heater itself.

When a leak means replacement, not a repair

Some leaks are genuinely small repairs. A dripping relief valve, a loose union, or a failed drain valve can often be swapped without touching the tank. A leak from the body of the tank is another story. Once the inner lining corrodes and begins to weep, there is no reliable fix, and the unit is on its way out.

Age is the tell. If a tank-style heater is well into its expected service life and the tank itself is leaking, most homeowners are better served replacing it than chasing a repair that will not hold. A professional can confirm the source and tell you honestly which situation you are in.

What to have ready when you call

A plumber can move faster when you can describe the unit. Before you call, jot down:

A photo of the label and the leak, sent ahead, helps too. Many of the plumbing and water heater companies listed in this directory offer same-day and emergency service, so help is rarely far away.

Stay calm and let a pro finish the job

Handling a leaking water heater at home comes down to a few safe, reversible steps: cut the energy, stop the water, drain if needed, and dry out the area. Those actions protect your home without putting you at risk. Leave the diagnosis and the new install to a licensed professional, who can also check the relief valve and venting on the replacement so the next unit starts its life safely.