no the vent pipe for the feed and expansion system should be a minimum of 450mm (dry head). for an open vent from a hot water cylinder it is 150mm PLUS 40mm per metre from the cistern to the bottom of the hot water cylinder.
Ok thanks for your repsonse.
The reason i ask is because in a plumbing book, by Treloar, which I have, it says the circulating pump should be the pump head (eg 5M) divided by 3 below the feed and expansion cistern's water level, to prevent undue movement in the cistern.
I've just moved into my new flat and notice that the pump is in the airing cupboard, and the hot water cylinder and feed and expansion tank are in the cupboard also. the pump is a wilo, and has 5m head. i don't think the feed cistern water level is 1/3 of that above the pump! does this mean...