Water leaking from flue?

[M.Joshi]

Hello,

We have recently had a new Vaillant ecoTec boiler and central heating system fitted.

Whenever the system is on, a stream of water drips from the flue outside occasionally?

What is likely to be causing this and is it easy to sort out?

Thanks.

[Chris Lewis]

According to M.Joshi :

Probably condensation of water vapor in the exhaust. This is probably entirely normal - especially so if the unit is high efficiency and the flue is plastic pipe.

Call the installer and ask.

[M.Joshi]

I thought that the condensed water vapour was supposed to drain via the two drainage pipes from the boiler and not the flue?

[Chris Lewis]

According to M.Joshi :

Much of it does, however, they don't extract _all_ of the water vapor, and the exhaust is continues to cool as it goes thru the pipe and hits outside yet colder air. Meaning condensation continues to occur right to the flue outlet.

Basically, whereever the exhaust is colder than the dew point w.r.t. humidity, condensation will occur. The drainage lines are for those portions of the exhaust path _inside_ the equipment, the plastic flue acts as drainage for the portion of the exhaust path outside of the equipment (path from the equipment to outside).