water dripping from vent pipe

[trentman]

when the water is being heated ,hot water is dripping from the vent pipe into the expansion tank,no water is being produced when rads are being heated.the tank does not overflow .the only reason i noticed is that the tank is above my bedroom and i`ve not noticed it before.is this normal or is there a problem ?thanks

wall mounted baxi fan flued gas boiler

 

[jobloggs]

It's quite common but it should not be happening.
Can you turn your pump down?

 

[trentman]

i turned it down to number 2 yesterday but i`ve not had time to listen to whether or not its cured the problem.do you think somethings restricting the flow around the hot water circuit and causing a back pressure forcing water up the vent pipe,thanks

 

[jobloggs]

Thats usually the problem as the vent is teed of the flow to the coil.
With the heating on the head of water does not build up to the same level.
However usually the pumping over is more of a flow than dripping.

Are your radiators heating up OK? Cooler spots at the bottom would indicate some sludging up of the system.

How high is the highest point of the vent pipe above the water level in the feeder tank?

 

[trentman]

the pipes are teed onto the feed from the boiler in the following ascending order,1-vent pipe ,2-cold water feed from header tank,then comes the pump and three port valve.

the water has stopped dripping from the vent pipe since i`ve turned the pump down.

the rads are warming up ok