what height should my vent pipe be above my feeder tank

[Guzzles]

Hi,

I have a grundfos super selectric 15-60. If I have it on speed 2 everything works fine, but I get water trickling back into the feeder tank via the vent pipe. If I have the pump on speed 1 the boiler temp trips out on CH and HW. I have been into the loft, and the height of the vent pipe is 18" above the water level. The Grundfos web site has lots of info, but nothing about the vent pipe height. The original pump was a 15-50, so I'm wondering whether the plumber should have checked the vent pipe height before upgrading my pump to a bigger one (the original was noisey). Is there a standard height for domestic installations?

 

[holty]

is the vent pipe after the pump

 

[JohnD]

you may have a lot of sediment in the system impeding flow. When you bleed the rads, is the water black?

Do you know where the drain cock is?

 

[werewolf]

could be caused by vent being incorrectly positioned in system or build up of sludge/muck .This could have caused pump failure in the first place.
Did you get to see old pump? was it full of sludge?Have you had circulation probs to rads downstairs/

 

[Agile]

A typical height for a vent pipe is about 300-400 mm above the water level.

This is only satisfactory if the pipework is totally correct.

Any sludge rapidly cause a pump over and then its all seriously downhill and gets worse by the hour!

Tony

 

[wilhelm]

then its all seriously downhill and gets worse by the hour!

which applies to everything in the uk ....

logic says bang a 15-50 on. and see wot happenz

 

[Guzzles]

The vent pipe and expansion tank feeder are located before the pump, and the pump is the right way round. Systems was flushed in the last year and plenty of inhibitor added. If you drain a low point in the system you get a little sediment, but soon clears. So it appears from previous replies that 300mm-400mm is the normal height of the vent pipe above the expansion tank water line - anyone dispute/confirm that?