Discovering a puddle of water near your water heater is alarming. But not all water heater leaks are equal — the response depends entirely on where the water is coming from. Here is a systematic guide to diagnosing and responding to a water heater leak.
Before doing anything else, dry the area completely and use a flashlight to trace the water back to its source. The location of the leak determines everything that follows.
The inlet and outlet connections at the top of the unit are among the most common leak locations. Over time, the fittings can loosen or the dielectric unions can corrode. This type of leak is almost always repairable — tightening the connection or replacing the fitting typically resolves it. Shut off the cold water supply, dry the fittings, and check whether tightening with a pipe wrench stops the leak. If it persists, the fitting or union needs replacement — a straightforward repair for a licensed plumber.
A dripping T&P valve typically means one of two things: the valve itself is worn and not seating properly (fix: replace the T&P valve — a $20–$50 part), or the system pressure is genuinely elevated above the valve's threshold, which causes it to weep. The latter situation usually means you have a closed plumbing system without an expansion tank. Replacing the T&P valve without addressing the root cause will result in the new valve dripping too. An expansion tank installation resolves the pressure issue permanently.
The drain valve at the bottom of the unit is used for flushing and maintenance. These plastic valves sometimes drip at the base or stem. If the leak is minor, attaching a garden hose cap over the valve opening is a temporary fix. Long-term, the drain valve should be replaced — a $5–$15 part that screws on. Not a reason to replace the unit.
Critical distinction: Condensation on the outside of the tank is normal and can pool on the floor. This is most common when cold water fills the tank in a warm, humid environment and does not indicate a problem. Dry the area and monitor — if the water reappears from a specific point rather than the overall tank surface, it is a leak rather than condensation.
If water is coming from the tank body itself — from the side, bottom, or through the insulation — this is a catastrophic failure. The tank has corroded through from the inside and cannot be repaired. Immediate action:
Do not attempt to patch or seal a leaking tank body. The structural integrity of the tank is compromised and the failure will worsen rapidly.
A small leak from a connection or valve gives you some time — hours to a day — to arrange a repair. A leaking tank body is an immediate problem. Hot water can cause significant flooring and subfloor damage within hours, and a tank that has begun to fail can fail completely without warning. Book a same-day replacement through WaterHeaterMan and start protecting your floor while you wait.
Enter your address and get an exact installed price for your home in under 60 seconds.
Get your price now →