Conventional vented system, header tank. Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[telstar]

I have a single level/floor flat with only four radiators, however air is getting into the system somehow. One radiator in particular needs bleeding daily as it feels warm less than half way up on a daily basis. One other radiator needs bleeding daily but to a lesser extent? New pump fitted recently by self. Where is all this air coming from, or just as worryingly, where is the water going, no sign of leaks (above floor level). Any suggestions would be welcome.

[Steve the gas]

Hi,

If you have speed settings on your pump - turn speed down to 1 or 2 and check results.
Also find small header tank - has it got any water in it.
I'm guessing it's pumping over and going out of overflow.

Hth

[telstar]

Thanks for that. The pump is marked I, II and III and it is at present on I which I take to be the slowest setting ie' 1. The header tank does have water. Tonight I bled the rads , switched on the heating and watched. I did observe water coming out of the vent pipe into the tank (about a cup full) while I was watching. So if the pump is on the slowest setting, is it too powerful for my system? I replaced it 'like for like' recently, it's a Grundfos 15-50

Many thanks.

[aceone]

yes i agree with steve turn pump down

[telstar]

Having read John Reginalds book 'Central Heating' I am convinced my system is suffering from 'see-sawing'. The book states "If the vent pipe is high enough (1.33 x pump head) should work without problems"
Can anyone tell me what 1.33 x pumphead means?
Many thanks.

[norwich-plumber]

silly ? but did you put the pump facing the same way as the old one .
if its pumping over on the slowest setting you will need to extend the heating expansion pipe

[telstar]

Yes, the pump is in the same direction and was a like for like replacement. I think this problem has been in place for a long time, I'm new to the property. I can't raise the vent pipe, it's a flat and it's already at ceiling height. Many thanks.

[rosebery]

"if its pumping over on the slowest setting you will need to extend the heating expansion pipe"

Unless there's a blockage in the pipework?

[Steve the gas]

Blow down the vent pipe.