megaflow with groundfos pump making pumping noises

[coreservers]

we have a megaflow cl148 cylinder and attatched is a grounfos alpha pump. all last night the pump was making a rythmic pumping noise spo loud it could be heard outside the back door of the house. which finally stopped at 08.30am 10 hours after startiing. it's in the airing cupboard, so we removed everythin g from there. it started again whne the central heating went on at 7pm, but this time the actuator valve reset automatically and it stopped the pump. I also noticed that when "pumping" the green power light on the groundfos flickered.

anything we can do to stop it?

 

[gremlin16]

all last night the pump was making a rythmic pumping noise

Was it a slow, medium or fast rythmic pumping noice.

 

[coreservers]

quite difficult to describe..... was roughly every 1-2 seconds, water pressure looks ok at 3 bar.

 

[gremlin16]

Sounds like the rotary positive displacement valve is producing negative feed.

 

[coreservers]

just found out the watermain near us burst, and is being repaired now, as all water has gone off. could this have affected it last night? if it was in the process of bursting?