Why Is My Water Heater Leaking?

by the Berry team · Updated October 20, 2026

Most water heater leaks come from a loose pipe connection, the drain valve, or the temperature and pressure relief valve, and those are usually repairable for a few hundred dollars or less. If the water is coming from the tank itself, the tank has rusted through and the only real fix is replacing the water heater.

Likely causes and what they cost to fix

Ordered roughly from most to least common for a tank water heater. Where the water is coming from tells you which row you are in, so see how to find the source below if you are not sure.

Cause	How to recognize it	DIY cost	Pro cost
Condensation, not a leak	Small puddle or drips under a gas unit, mostly when it first heats a tank of cold water. Stops once the tank is warm.	DIY$0	ProNo repair needed
Loose or worn pipe connections on top	Water on top of the tank or running down the side from the hot or cold line fittings.	DIY$10-$40 for new supply connectors	Pro$150-$350
Drain valve dripping	Drips from the spigot near the bottom of the tank, often after someone has flushed it.	DIY$5-$25 for a hose cap or new valve	Pro$100-$250
Relief valve leaking or discharging	Water from the temperature and pressure relief valve on the side or top, or from the pipe that runs down from it.	DIY$20-$40 for a new valve	Pro$150-$350
High water pressure or thermal expansion	The relief valve drips repeatedly even after it is replaced. Common if your home has a pressure reducing valve or check valve and no expansion tank.	DIY$40-$80 for an expansion tank, if you are comfortable plumbing it in	Pro$200-$500 to add an expansion tank
Tank rusted through	Water pooling under the tank with no wet fittings above it, often with rust stains. Most common on older units.	DIYNot recommended	Pro$1,200-$3,000 to replace the water heater

Ranges are typical US prices and vary with your region, your home, and the season. A pro quote for your exact job beats any range.

First, make it safe

A leaking water heater is rarely an emergency in the first hour, but water and electricity or gas do not mix. Do these before you start investigating:

Cut the heat. If it is electric, turn off its breaker at the panel. If it is gas, turn the control knob to "Pilot" or "Off."
Shut off the water to the tank. Close the valve on the cold water line that feeds the top of the heater. If that valve will not turn or there is no valve, close your main water shutoff.
Protect the floor. Put down towels or a shallow pan, and move anything stored nearby that can be damaged by water.
Only drain the tank if the leak is from the tank itself. Attach a garden hose to the drain valve, run it to a floor drain or outside, and open a hot water tap somewhere in the house so air can get in. The water is hot, so give it time to cool first if you can.

How to find the source

Water runs down and collects at the bottom, so a puddle under the tank does not mean the tank is leaking. Dry everything with a towel, then watch for where water shows up first.

Check the top. Look at the hot and cold connections, the flexible supply lines, and the shutoff valve. Run a dry paper towel around each fitting. If the towel gets wet, you have found it, and it is usually the cheapest fix on this page.
Check the relief valve. It is a lever valve on the top or upper side of the tank with a pipe running down toward the floor. Water at the end of that pipe means the valve is opening. Occasional drips can be a worn valve. Steady discharge points to high pressure or temperature.
Check the drain valve. Near the bottom of the tank. Make sure it is fully closed by hand. Plastic drain valves often start dripping with age, and a brass hose cap is a cheap stopgap until it is replaced.
Check around the tank. Look for water coming from nearby pipes, a furnace or AC condensate line, a water softener, or anything above. Water heaters get blamed for a lot of leaks they did not cause.
Rule out condensation. If you have a gas water heater and the drips appear right after a lot of hot water use, then stop once the tank warms up, that is usually condensation, not a leak.
If everything above is dry. But water still collects under the tank, the inner tank has most likely corroded through. A corroded tank cannot be patched.

Repair or replace?

If the leak is from a fitting, a valve, or the drain, repair it. Those are inexpensive parts and fixing them does not shorten the life of the heater.

If the tank itself is leaking, replace the water heater. Leaks from the tank do not get better, and a tank that has started to fail can let go with much more water than a slow drip. Tank water heaters often last somewhere around 8 to 12 years, depending on water quality and maintenance. If yours is near or past that range and needs a repair, it may make more sense to put that money toward a replacement. See how long a water heater lasts for how to find its age from the serial number and what shortens or extends it.

If you have a tankless water heater, leaks usually come from fittings, the pressure relief valve, or internal components. The fixes are different and usually a job for a pro who services that brand.

How to prevent the next leak

If you have a tank water heater, flush a few gallons from the drain valve once a year to clear sediment.
Check your home water pressure with a $10-$15 gauge on an outdoor faucet. Readings above about 80 psi are worth talking to a plumber about, since high pressure is hard on the tank, the relief valve, and every fixture in the house.
Put the water heater in a drain pan if it sits anywhere a leak would damage finished floors or ceilings below.
Consider a leak sensor ($15-$50) next to the tank. Water heaters usually sit where no one looks, and a sensor tells you about a drip the day it starts.

When to call a pro

Water is coming from the tank itself rather than a fitting or valve.
The relief valve keeps discharging, or is discharging hot water or steam.
You smell gas, or see scorching or soot around the burner area of a gas unit. Leave the house and call the gas company from outside if you smell gas.
The leak is near electrical wiring or the heater is electric and water has reached the controls.
You need to replace the water heater. Gas venting, electrical, and permit requirements make this a pro job for most people.

What makes it worse if you wait

A tank leak only goes one way. A slow drip can turn into a sudden failure that releases far more water than a towel can handle.
Even a small leak that runs for weeks can rot a wood subfloor, wick into drywall, and start mold growth.
A relief valve that is discharging is a safety device doing its job. Ignoring it, or capping it, leaves the underlying pressure or temperature problem in place.
Replacing a water heater on your own schedule lets you compare quotes. Replacing one after it floods the basement does not.

Common questions

Is a leaking water heater dangerous?

A slow leak is usually more of a water damage risk than a safety risk. The exceptions are a relief valve that keeps discharging hot water or steam, any smell of gas, and water reaching electrical parts. In those cases, cut the power or gas and call a pro.

Can I still use a water heater that is leaking?

If the leak is a small drip from a fitting or the drain valve, you can usually keep using it for a short time while you get it fixed. If the tank itself is leaking, shut it off and drain it, because tank leaks can get much worse without warning.

Why is my water heater leaking from the bottom?

Water at the bottom can come from the drain valve, from a leak higher up that ran down the side, from condensation on a gas unit, or from the tank itself. Dry everything and check the top fittings and relief valve first. If those are dry, the tank has likely failed.

How much does it cost to fix a leaking water heater?

Fixing a loose connection, drain valve, or relief valve typically costs $100-$350 with a plumber, or much less if you do it yourself. If the tank is leaking, replacing a standard tank water heater usually runs $1,200-$3,000 installed, depending on size, fuel type, and local code requirements.

Is it normal for the relief valve to drip?

No. An occasional drip can mean the valve is worn and needs replacing. Repeated or steady discharge usually means the water pressure or temperature is too high, often from thermal expansion. Have a plumber check the pressure and whether an expansion tank is needed.

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