A small pipe dripping outside can be easy to ignore because the water is not entering a room. But it may be an overflow warning from a storage tank or a discharge from a boiler or hot-water system. The pipe's position alone does not prove which system is at fault.
An overflow or safety discharge needs a clear route out. Do not plug, tape or reroute it to stop the drip. Water from a heating discharge may be hot, so keep clear of the outlet.
What can the pipe be connected to?
- Storage tank or cistern
- An overflow warns that the water level is too high, often because an inlet valve is not closing properly. A plumber can trace and repair the cause.
- Boiler or hot-water safety discharge
- A pressure relief device can send water outside. A persistent drip or flow needs a heating engineer to inspect the system and its safety controls.
- Condensate drain
- Some boilers normally release condensate through a separate drain while running. Do not decide that a new or continuous leak is harmless from a photo alone.
Safe observations before you call
- Take a photo showing the outlet and the wall around it
- Note whether it drips only while heating or hot water is running
- Record whether it is a slow drip, frequent trickle or steady flow
- Look for a boiler pressure warning on its normal display without opening the casing
- Check whether water is also appearing inside or near electrical fittings
When should it be treated as urgent?
Arrange prompt help if the flow is continuous, the water is hot, the boiler shows a pressure fault, or an internal tank or ceiling is wet. Keep people away from a hot outlet. If water reaches electrics, avoid the wet area and seek urgent help. A persistent outside drip still deserves inspection even if the house looks dry.
WaterSafe's home water guide explains why storage tanks need a visible overflow. Vaillant's homeowner guide describes how a boiler pressure relief valve can discharge outside. For an unclear leak, see our leak detection guide; for an active overflow, request an emergency plumber or a heating engineer if the pipe serves the boiler.