Short answer: Find where the water is coming from. A leak at the cold or hot connections on top, or at the drain valve, can usually be repaired. Water from the temperature and pressure (T&P) relief valve means the tank may be overheating or over-pressurized: turn the heater off and call a plumber. Water seeping from the tank body or under the base usually means the tank has failed and must be replaced.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Drip from pipes on top | Loose fitting or corroded connector | Wipe dry and watch | Often |
| Water from the relief valve pipe | Overheating, high pressure or worn valve | Is the discharge pipe dripping or spraying? | Yes, promptly |
| Drip at the drain valve | Valve not fully closed or worn | Check that it is closed; look for a cap | Sometimes |
| Puddle under the tank, no visible source | Tank corrosion | Dry everything and inspect | Yes, usually replacement |
| Water near the heater but not from it | Condensation or another pipe | Check nearby pipes and the AC drain | Depends |
Make it safe
- Turn off power at the breaker (electric) or set the gas control to off or pilot (gas).
- Close the cold water supply valve on top of the heater.
- Protect the floor and anything nearby from water.
Leak from the tank means replacement
A. O. Smith states that a heater leaking around the base of the tank is probably due for replacement, while leaks from faulty valves or loose connectors can often be fixed. A. O. Smith also puts the average life of a water heater at 8 to 12 years.
The relief valve
The T&P valve opens to release water when temperature or pressure gets too high. Occasional drips can come from thermal expansion, but steady discharge is a warning. Do not cap or plug the relief valve pipe. A plumber should check the thermostat, the system pressure and whether an expansion tank is needed.
When to call a professional
- The tank itself is leaking.
- Water is coming from the relief valve.
- You cannot safely shut off gas or power.
- The heater is old and showing rust or noise.
What it usually costs
HomeGuide (2026) lists a T&P valve replacement at about $50 to $300 and a new tank water heater at about $600 to $1,800 installed.
Frequently asked questions
Is a leaking water heater dangerous?
A slow fitting leak mostly causes water damage. Water from the relief valve can signal overheating or excess pressure and should be checked promptly.
Can I still use my water heater if it is leaking from the bottom?
A leaking tank usually cannot be repaired. Shut it off and plan a replacement.
Related problems
- No hot water
- Hot water smells like rotten eggs
- Pipes banging (water hammer)
- Water stain on the ceiling
Sources
- A. O. Smith: When to repair or replace your water heater
- Rheem: How often to flush your water heater
- HomeGuide: Water heater repair cost (2026)
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.