Plumbing guide
Water heater leaking: what it means and what to do
By the Home Doctor team · Reviewed
Quick answer
Most water heater leaks come from one of four places: the temperature-and-pressure (T&P) relief valve, the drain valve near the bottom, the pipe connections on top, or the tank itself. Leaks from valves and fittings are usually fixable with a part under $50. Water coming from the tank body means it has rusted through and needs replacing, typically $1,200 to $3,500 installed for a standard 40 to 50 gallon tank.
- How urgent
- Urgent
A slow drip from a fitting can wait a day or two if you catch the water. A leak from the tank itself only gets worse and can let go suddenly.
- DIY or pro
- DIY if handy
Tightening fittings and swapping a drain valve or supply connector are handy-homeowner jobs. Replacing the tank usually needs a permit and a plumber.
Stop and call a pro now if
- Gas heater and you smell rotten eggs: leave the house and call your gas utility from outside.
- Water pooling near the electrical connections of an electric heater: switch off its breaker before you touch anything.
- The T&P valve is blowing hot water or steam: stay clear, shut off the power or gas, and call a plumber. The tank may be overheating.
Common causes and how to tell them apart
1. T&P relief valve
- How to tell
- Water runs from the discharge pipe on the side of the tank, or the valve itself is wet.
- What fixes it
- An occasional drip can mean the valve is worn. Frequent discharge means pressure or temperature is too high, often from high street pressure or a missing expansion tank.
2. Drain valve
- How to tell
- Drips from the hose spigot near the bottom of the tank.
- What fixes it
- Snug it closed and add a hose cap. If it still drips, replace the valve.
3. Loose connections on top
- How to tell
- Water on top of the tank or running down from the hot or cold pipes.
- What fixes it
- Tighten the fittings. Replace corroded flex connectors.
4. Condensation
- How to tell
- A little water under a gas heater, mostly after a lot of hot water use or when first filled. It stops once the tank is hot.
- What fixes it
- Nothing to fix if it stays small and stops. Keep watching it.
5. Tank corrosion
- How to tell
- Water seeps from under the jacket or the bottom of the tank, sometimes with rusty water. Often in tanks 8 to 12 or more years old.
- What fixes it
- The tank can't be repaired. Plan a replacement.
Not sure which one you have?
Snap a photo. Home Doctor narrows it down, tells you how urgent it is, and prices the fix.
Diagnose it from a photoFirst diagnosis free. No account needed.
What you can safely try first
- 1Dry everything with a towel, then watch for 10 minutes to see where water appears first.
- 2Turn off the cold-water supply valve on the pipe going into the heater.
- 3Turn off the breaker (electric) or set the gas control to Off or Pilot (gas).
- 4Put a drain pan or towels down, and check the label for the tank's age.
When to call a pro
- Water is coming from the tank itself.
- The T&P valve keeps discharging.
- You can't find the source of the leak.
- Any gas smell, scorching or water near wiring.
What it costs
| Job | DIY parts | Pro, installed |
|---|---|---|
| Replace T&P relief valve | $20–$40 | $150–$350 |
| Replace drain valve | $10–$25 | $100–$250 |
| Replace supply connectors | $10–$30 | $100–$250 |
| Add a thermal expansion tank | $40–$80 | $200–$450 |
| Replace a 40–50 gal tank water heater | Not recommended | $1,200–$3,500 |
Ballpark US ranges as of September 27, 2026. Your region, access and the specifics of your home can move these a lot. Get two or three quotes for anything over a few hundred dollars.
What to tell the pro
My [gas / electric] tank water heater, about [age] years old, is leaking from [the top fittings / the relief valve / the drain valve / under the tank]. I've shut off the cold supply and the [breaker / gas]. Can the valve or fitting be replaced, or is the tank failing? If it needs replacing, does your price include the permit, haul-away and any code updates like an expansion tank?
Questions people ask
Is a leaking water heater an emergency?
Not always, but don't ignore it. A drip from a fitting or valve can usually wait a day or two if you catch the water. A leak from the tank itself means it's failing, so shut off the cold supply and the power or gas and get it replaced soon.
Can I keep using a leaking water heater?
If the leak is a small drip from a top fitting or the drain valve, usually yes, for a short time while you fix it. If the tank itself is leaking, shut it down. A rusted-through tank can fail and flood.
Why is water coming out of the pressure relief valve?
The valve opens when tank pressure or temperature gets too high, or when it's worn out. Common causes are the thermostat set too high, high water pressure from the street, or a missing or failed expansion tank. A valve that discharges more than once needs a plumber to look at it.
How long does a tank water heater last?
Typically 8 to 12 years. Hard water and skipping the yearly flush shorten that.
Get an answer for your house
Every house is different. A photo gets you the likely cause, how urgent it is, and a fair price, in about 30 seconds.
Diagnose it from a photoFirst diagnosis free. No account needed.
General guidance, not a substitute for a licensed professional who can see the problem in person. If you smell gas, see sparks or smoke, or anyone is hurt, leave the area and call 911.