Open system water volume

[mazme]

Can anyone tell me roughly the water volume of a typical c/h system with 7 rads. I know it wont be exact but an estimate wiould be useful. I understand there should be 3% of the sytem volume in the feed pipe to prevent air being drawn in. I have 2m of 22mm cold feed pipe from the tank to the highest point of the system; I'm trying to find out if the tank needs raising.

thanks a lot

mazme

 

[ChrisR]

It'll usually be a fair bit less than the 100 litres we bung inhibitor in to cover. Especially if your radiators are convectors.

 

[JPC]

i see your in gwynedd....7 rads....78 litres

 

[mazme]

thanks for the swift reply ChrisR

all convectors and fairly small house so should only be about 3 litres needed then.

Is it permissable to drop the cold feed pipe to the floor and then back up to increase the head?

mazme

 

[D_Hailsham]

Is it permissable to drop the cold feed pipe to the floor and then back up to increase the head?

It will not make any difference to the head, which is determined by the height between the water level in the tank and highest point, not by the length of pipe between the tank and the highest point.

If you need to increase the head you will have to raise the tank.

 

[mazme]

thanks for the reply D_Hailsham

now I think about it, silly thing to say

it's just difficult raising the tank in the loft so trying to find other ways of increasing the head. May well be enough but I seem to be getting air in somewhere. Pump vertical and flowing downwards so perhaps that doesn't help.

mazme