Pump turning, but water not moving!

[simonking087]

Hi folks, should I just fit a new pump? I have checked that the pump is turning but the rads are only getting hot via gravity. If the heating is left on all day the rads do eventually get warm, the trouble is that the boiler thinks the water is hot enough and then shuts down, the water is just not shifting, I do not think it is a blockage, otherwise all the rads would not get warm. Any advice?

 

[PlumbBobBob]

is the pump upstairs and upstairs rads get hot but not downstairs?

 

[ADM360]

as steveb said is it upstairs? could be an air lock after the pump!

 

[simonking087]

thanks for the reply's. The rads after four hours do get luke warm all over, the ones nearest the hot water tank get warm first, it is a conventional boiler, but some of the pipework is microbore, it just seems that the pump is not pushing the water round fast enough. The pipes at the tank are really hot, the boiler thinks the water is hot and then turns off, as a consequence the house is freezing! The pump is upstairs at the hot water tank.

 

[secret squirrel]

If you drained the system down to change the pump it sounds like an air lock. Have you got any air vents that could be bled, automatic air vents anywhere? bled then re-bled the rads?

If you search on the forum about airlocks then you'll get loads of hits! everything anyone has ever come across to do with air locks has been written on the forum.

 

[simonking087]

Thanks secret squirrel, yes I have bled everything, but as yet have not changed the pump. I was thinking if I opened the drain off valve and then turned the pump on, I could then tell if the pump was improving the pressure, if no or very little change then the pump could be the problem.

 

[secret squirrel]

Its early, misread your post, thought you'd changed your pump.

Providing everything else is working, the two or three port valve is opening correctly, just change the pump. You can get a pump for about £40 don't forget to put inhibitor into the system

 

[simonking087]

I think that is the best option, I could be mucking about with it all day and the decide to change the pump just after the supplier has closed, thanks for the help. Cheers

 

[PlumbBobBob]

there should be isolators each side of the pump just close these then no need to drain down. should be max of about pint of water just have plenty of towels to catch it. of course if the isolators are stuck or don't turn off you will have to drain down then.

 

[simonking087]

I am expecting the isolators to be stuck, the whole system is a nightmare and will be glad to see the back of it, I have never had a job go well when I have worked on it, there are always more problems than I had expected and am sure that will not change this time. Thanks for all the advice, I may be back on later saying "pump changed, now what?" let's hope not!