central heating

[bruce 1411]

i have a gravity and pump fed indirect system (no 3 port valve) can anyone tell me why it would suddenly start sucking air? some time ago i removed the sludge from the system "it was bad" and ever since i have had to take an air lock out at the top tee return to the f&e tank in the loft average once a fortnight.
the c.h. feed from the loft (bottom pipe on side of the cylinder) is not perfectly horizontal but we've lived here over 20 years and this has not happened before, im thinking of draining the whole system and replacing the gate valves with full bore lever valves then refilling bleeding and shutting off the c.h. valve but i still wont know whats causing it

 

[Agile]

I cannot follow your description.

It sounds as if you have a blockage or layout problem.

A gate valve is virtually full bore anyway!

Tony

 

[John506]

Could it be taking air in from the vent pipe?

 

[gas4you]

Go into the loft with a jam jar. Fill it with water and place over the open vent on the ch.

Get someone to turn on the heating and see if the water in the jar is sucked up the open vent.

If it is it is sucking in air from here due to a fault/blockage in the system somewhere.

 

[bruce 1411]

thanks guys sorry its taken so long to get back, i'll try the jamjar idea, if this helps i have one rad in the living room that keeps packing up and when i run the pump i have to remove the air every week as opposed to fortnightly