Water dripping from inside the boiler casing: where it usually starts

Water inside the boiler casing: the short technical version

The plate heat exchanger, the automatic air vent on top of the pump, and internal pipe seals that harden with age over many heating seasons are the three most frequent internal sources on a combi. A failed pressure relief valve seat can also weep internally before it ever reaches the external discharge pipe. Because these components sit close together, an engineer dries the area fully and re-runs the boiler under observation to catch the drip at its actual source.

Detail that affects your quote for water inside the boiler casing

• Internal moisture differs diagnostically from pipework-level leaks
• The plate heat exchanger is a common internal leak point on combis
• The automatic air vent on the pump can weep as its seal ages
• Old internal pipe seals harden and lose their grip over time
• The area is dried and observed under running conditions to confirm the source

Questions we get asked

Can I open the casing to look myself?

The casing is safe to remove for a visual check, but do not touch internal components with the boiler powered.

Is an internal leak always a big repair?

Not necessarily — a hardened seal or an air vent is often a modest, quick fix once correctly identified.

Where we deal with this

• Cranmore (BA4) · 8 mi
• Priddy (BA5) · 12 mi
• West Pennard (BA6) · 13 mi
• Trudoxhill (BA11) · 8 mi