Water heater leaking? Where it leaks tells you how serious it is
Quick answer
Where the water heater leaks tells you how serious it is. A leak at the top is usually a loose or corroded inlet/outlet connection — often fixable. Water from the temperature-and-pressure (T&P) relief valve can be a normal pressure release or a faulty valve. A leak from the bottom of the tank body usually means the tank is corroding from the inside and can't be repaired — only replaced. If it's leaking significantly, shut off the water supply and the power or gas to the heater.
Common causes
- Loose or corroded inlet/outlet pipe connections at the top of the tank.
- The T&P relief valve discharging — from thermal expansion/overpressure, or a faulty valve.
- A dripping drain valve at the base.
- Condensation running down the tank (common on gas units) — not always a true leak.
- Internal tank corrosion causing a leak from the body — a tank that can't be repaired.
What to check first
- Dry everything, then watch to pinpoint the source: top connections, the T&P valve, the drain valve, or the tank body.
- Top connection: try tightening or resealing the fitting.
- T&P discharge: frequent release can mean overpressure that needs an expansion tank, or a worn valve.
- Base of the tank: a leak from the body itself usually means the tank is failing — plan to replace it.
- Shut off the cold-water supply valve to the heater if it's leaking and you'll be away.
When it's urgent
A tank leaking from the body can go from a trickle to a flooded floor with little warning — shut off the water supply and the power or gas, and plan replacement promptly. A T&P valve releasing hot water or steam means an overpressure condition to take seriously. Any smell of gas means leave the house and call your utility.
DIY vs. call a pro
You can likely DIY
- Tightening or resealing top pipe connections.
- Replacing a dripping drain valve, with care.
- Telling condensation apart from a true leak.
Call a pro for
- Replacing the tank — especially gas units (gas line + venting).
- Recurring T&P discharge that needs an expansion tank or valve work.
- Any leak from the tank body, or if you're unsure of the source.
Estimated cost range
How HouseCue helps
HouseCue is a private, homeowner-first app that turns this from a one-time worry into a tracked plan. Snap a photo for an AI diagnosis, upload your inspection report to auto-build a handbook, and get seasonal reminders for your roof, HVAC, water heater, plumbing, and electrical — so nothing slips. Connecting with a pro is always optional and only when you choose.
Get started freeFrequently asked questions
Is water under my water heater an emergency?
It depends on the source. A dripping valve or condensation is not urgent, but water leaking from the tank body can fail suddenly and flood the area — shut off the water and power/gas and replace it promptly. Always identify where the water is coming from first.
Why is my T&P relief valve leaking?
The temperature-and-pressure valve releases water when pressure or temperature gets too high. Occasional dripping can be normal thermal expansion (often solved with an expansion tank), but frequent or hot discharge can mean overpressure or a failing valve — have it checked.
Can a leaking water heater be repaired?
Leaks at valves and fittings can usually be repaired. But once the steel tank itself corrodes and leaks from the body, it can't be fixed — the unit needs replacement.
Related guides
HouseCue guides are general educational information, not professional inspection, engineering, or contracting advice. Costs vary by market. For safety issues — gas, electrical, structural, or major water — contact a qualified professional.