Grundfos pump getting air in

[superhondaman]

Hi i have a grundfos 15/60 about 6yr's old, recently i have had to undo the bleed screw every morning to get hot water running through the pipes. It takes about 30 sec for the water to start dripping out and the pump then becomes noisy but the rads heat up. i have checked all the joints around the pump and valves with a w/up soloution and there does not apper to be any leaks. This only seems to happen when the heating has been off e.g. on timer or i have tried leaving thermostat on low over night but they are still cold in the morning and i have to vent the pump again. Any ideas?
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lynda, moderator

your title has been edited, see forum rule 5

 

[ChrisR]

Is the pump in a high point in the system?

 

[superhondaman]

The pump is fitted in the airing cupbord upstairs about 90cm below the expansion tank in the loft directly above.

 

[ChrisR]

WHat I mean is, is it in a section of pipe which could collect air from the pipework when the pump is off? Like an inverted U.

 

[superhondaman]

Above the pump is a joint on a 22mm t across to the vent pipe feeding into the expansion tank via an inverted u