Boiling water in expasion tank

[EG]

The whole of the roof space is soaking wet with condenstion, roofer says it major plumbing problem , had new boiler 2 years ago cylender, under floor heating. and some new rads. We have had broblem with getting hot water on its own it takes for ever to heat up, radiaters and under floor heating is find.
No one has been in roof for 2 years, as soon as CH is up to heat the vent pipe starts with a tricle of water then runs nearly at full bore making the attic space like a sauna. When we try and run hot water it makes the vent pipe pruduce even more hot water. both the vent and return always very hot.
Please help

 

[PEDANTICVINDICTIVEMAN]

 

[kevplumb]

read this first

 

[felix]

You are just one of many people on this forum with water gushing from their vent pipes so I can understand the reluctance of some old hands to keep answering the same question for the umpteenth time.

It's almost certain that your problem stems from badly plumbed feed and vent pipes. Quite simply, when the pump runs, the pressure in the vent pipe rises above that in the feed pipe with predictable results. I just know I've said all this before but here we go again ----

ON A FULLY PUMPED SYSTEM THE VENT AND FEED MUST BE ATTACHED VERY CLOSE TOGETHER ON THE SAME PIECE OF PIPE.

Let's hope everybody and his dog heard that! Find out where yours go and I bet you solve your problem. A search on this forum will reveal many similar cases.