Boiler is leaking water

Symptoms

• Puddle or damp area around the boiler base
• Dripping visible from a pipe, valve, or the unit itself
• Pressure gauge may be dropping alongside the leak

Likely causes

• CommonLeaking pressure relief valveThis valve can weep water if it's slightly worn or if system pressure is too high.
• CommonLoose or corroded pipe fittingFittings can loosen with age and vibration, or corrode and develop a pinhole leak.
• PossibleFailing internal seal or gasketInternal boiler components wear out over years and can start leaking.
• Less commonCracked heat exchangerA more serious and costly failure that usually requires full boiler or exchanger replacement.

What to do

1. Turn off the boiler and, if the leak is significant, shut off the water supply to the system.
2. Look for the exact source: check the pressure relief valve discharge pipe, visible fittings, and the boiler's base.
3. Place a towel or container to catch water while you locate the leak and prevent floor damage.
4. Check the pressure gauge; if it's unusually high, a relieving valve leaking may be a symptom of overpressure elsewhere.
5. Don't attempt to tighten fittings on a pressurized, hot system; let it cool and depressurize first if safe to do so.
6. Call a technician for anything beyond an obviously loose, cool, accessible fitting.

Tools and parts

• Towels
• Bucket

When to call a pro

Call a heating technician promptly for any leak beyond an obviously loose cool fitting; internal leaks can worsen quickly.

Safety