Why Is My Water Heater Leaking?
A leaking water heater usually starts at one of six spots: the fittings on top, the temperature and pressure (T&P) relief valve and its side pipe, the gas control valve, the drain valve, the tank itself, or water in the pan (often condensation on gas units). Fittings and valves are normally repairable. A rusted-through tank has to be replaced.
The fastest way to know which one you have is to find the first wet spot. Water runs down, so a puddle on the floor tells you very little on its own. A drip from a fitting on top can run down the side of the tank and look exactly like a bottom leak.
This page walks you through a simple top-to-bottom check. If you'd rather not look yourself, call us at +1 480-863-0807. We're open 24 hours, 7 days a week.
Safety first: if water is spraying, or you see water near an electrical outlet or panel, turn off the cold-water valve and the power before you look closer. If you smell gas, leave the house and call 911 and your gas company (Southwest Gas, or your propane supplier) from outside.
Before You Start: Stop the Water
You don't need to drain anything. Just slow the leak so you can see where it starts.
- Turn off the cold water to the heater. The valve is on the cold pipe above the tank. A lever handle goes crossways to the pipe. A round handle turns clockwise.
- Turn off the heat. Flip the breaker for an electric heater. Set the gas control knob to "Pilot" or "Off" on a gas heater.
- Dry everything. Wipe the tank, the pipes and the floor with a towel.
- Wait 10 to 30 minutes, then look again from the top down.
Our full step-by-step guide, including tankless units and mobile-home closets you reach from outside, is on the how to shut off a water heater page.
Where Is the Water Coming From? Check These 6 Spots
Work from the top of the heater to the floor. The highest wet spot you find is almost always your leak. Each row links to a page that covers that spot in detail.
| Where you find water | Most likely cause | How to confirm it | Usually |
|---|---|---|---|
| Fittings on top of the tank | Corroded nipple, worn flex connector washer, loose nut | A paper towel wrapped around the joint comes back wet | Repair |
| T&P valve or the pipe down the side | Worn valve, or pressure building with no working expansion tank | The open end of the side pipe is wet or dripping | Repair |
| Gas control valve on the front | Water getting out where the valve threads into the tank | Wet or rusty threads around the control box, everything above it dry | Depends on tank age |
| Drain valve near the bottom | Cracked plastic valve, worn washer, or sediment holding it open | Water drips from the spout, the handle or its threads | Repair |
| Bottom seam or behind the access panel | Inner tank has rusted through | Soggy insulation behind the panel, with every fitting and valve above it dry | Replace |
| Drain pan only, tank looks dry | Condensation on a gas unit, or a drip from something above | Water stops once the tank is fully hot | Often no repair |
What Each Leak Spot Means
Water on top of the tank
The cold inlet and hot outlet connect to short steel pipes called nipples. In our hard water, those nipples and the connectors on them corrode over time. You'll often see white or green crust, or a rusty ring, around the leak. A corroded nipple or connector usually needs replacing, but it's a repair, not a new heater, as long as the tank itself is dry. The top-leak page linked in the table covers each fitting.
Water on the pipes near the heater
If the highest wet spot is on a line a few inches or more away from the tank, the heater is usually fine. Soldered copper joints, PEX crimps, old valves and high house pressure are the usual causes. See our guide to leaks on the water lines around the heater.
Water dripping from the relief valve pipe
The T&P valve sits on the top or upper side of the tank, with a pipe running down toward the floor. Water from that pipe is the valve letting out pressure or heat. A slow, steady drip usually means a worn valve that needs a T&P valve replacement. Water that comes out now and then, often after heavy hot-water use or overnight while the heater reheats with no tap open, usually points to thermal expansion.
Water around the gas control valve
On gas heaters, the control valve threads into the front of the tank. Water around those threads can come from a failing seal or from corrosion in the tank wall behind it. On a young tank it can sometimes be fixed. On an older one, it's often the first sign the tank is wearing out, so it's worth taking a moment to weigh repair against replacement.
Water dripping from the drain valve
Many factory drain valves are plastic, and hard-water sediment can stop them closing fully. Replacing one with a brass valve is a common, inexpensive fix.
Water from the bottom seam or behind the access panel
Wet insulation behind the burner or element panel, or water under the outer jacket, means the steel tank has rusted through. A tank can't be patched safely, so this one means replacement. If the heat has quit as well, see leaking with no hot water.
Water in the pan, but the tank looks dry
Gas water heaters can "sweat" when cold water fills the tank, especially on cool winter mornings. That condensation dries up once the tank is fully hot. A real leak keeps going.
A heater that's only weeks or months old
On a new install, the tank is rarely the problem. Look at the connections made on install day, the drain valve and the relief valve first. Our page on a new water heater leaking covers what to check and what to save for a warranty claim.
Water under a tankless unit
Tankless heaters have no tank to rust through. Water under one usually comes from the isolation valves, a fitting, the pressure relief valve or a condensate line. See tankless water heater leaking and repair.
Is a Bottom Leak Always the Tank?
No. This is a very common mix-up. Water collects at the bottom no matter where it starts. A T&P valve pipe empties near the floor, a drain valve sits at the bottom, and a drip from a fitting runs down the tank wall. Only when those three are dry and the tank is still wet is it the tank. We cover this step by step on the water heater leaking from bottom page.
Tip: Tuck a dry paper towel under each fitting, the T&P pipe and the drain valve. Check them in 30 minutes. The wet towel points to the leak.
Why Water Heaters Leak Early in Apache Junction
Water heaters here wear out faster than in many parts of the country. A few local reasons:
Hard water wears out valves
At about 13–16 grains of hardness per gallon, local water drops a lot of sediment in the tank. That grit keeps drain valves from sealing and crusts up fittings and valve seats.
Garage heat hardens washers
July highs average about 105°F. Heaters in closed garages and outdoor closets sit in even hotter air, which is hard on relief valves, washers and flex connectors.
Monsoon rain and humidity
From June 15 to September 30, storm rain can run down a damaged vent cap onto the burner, and humid days make cold pipes sweat. Both can look like a leak. Outages can also trip the breaker or high-limit reset, so check those if the heat stops too.
How homes are built
Almost half the homes in town are mobile or manufactured homes. Many heaters sit in tight closets over wood floors or on wood platforms in garages, so a slow leak does damage quickly.
When Should You Call Instead of Checking Yourself?
- Water is spraying or pouring, not dripping
- The leak is near an outlet, the breaker panel or the gas line
- You smell gas or see scorch marks near the burner
- The heater is in a closet you can't safely reach or see into
- The shut-off valve above the heater won't close or drips at the handle (see shut-off valve replacement)
- The floor or wall is wet but you can't find the source (see leak detection)
- The floor near the heater feels soft or spongy
- You've found the leak but aren't sure if it's repairable
If water is spraying or pouring, shut it off and see our emergency leak help page. Valve and fitting repairs cost far less than a new heater. Angi's Apache Junction average for water heater repairs of all kinds is about $646, and our guide to what leak repairs usually cost here breaks it down.
Apache Junction Water Heater Pros handles leaks day and night from our office at 279 N Ironwood Dr. We'll find the real source, explain whether it's a repair or a replacement, and go over the price before any work starts. Learn more about our water heater leak repair service.
Water Heater Leaking FAQs
Is a leaking water heater dangerous?
A slow drip isn't usually dangerous in the first few hours, but it can damage floors and walls quickly. The real risks are water near electrical outlets, a gas smell, or a relief valve that's been capped. Turn off the water and the power or gas, and call if you're unsure.
How do I know if my water heater leak is serious?
It's serious if water comes from the tank body, the bottom seam, or the insulation behind the access panel, because that means the tank has rusted through. Leaks from fittings, the drain valve or the relief valve are usually fixable, though they still need attention soon so the floor and walls stay dry.
Why does my water heater only leak while it's heating?
Heating raises pressure and temperature inside the tank. If water appears at the relief valve pipe only during heating, thermal expansion is the likely cause. On a gas unit, water at the burner during a cold-tank heat-up is often condensation. A drip at a fitting that shows up when warm can be metal expanding at a loose joint.
Could the water be from my AC line or something above the heater?
Yes. Air conditioner condensate lines, supply pipes and even a sweating cold pipe can drip onto the heater and into the pan. Dry everything, then look above the heater first. If the tank and its fittings stay dry and only the pan is wet on a gas unit, it may be condensation. Dry the pan and watch: water that shows up only while a cold tank heats, then stops, is condensation.
Can a leaking water heater cause mold?
It can. Drywall, carpet and particleboard that stay wet for more than a day or two can start to grow mold. Stop the leak, pull wet items away, run fans and dry the area as soon as you can. Photograph the damage first if you plan to talk to your insurance agent.
Which water heater drips can safely wait a day?
A slow drip from a fitting, the drain valve spout or the relief valve pipe can usually wait a day or two with the cold water off and a bucket underneath. Check the bucket every few hours. Water from the tank body is different. A rusted tank can split without warning, so shut it down and plan the replacement right away.