Header tank supply

[Canary42]

Does the central heating header tank water supply have to be taken from the mains, or is it permissible for it come from the cold water storage tank ?

[RevArkwright]

Cannot see why it matters as long as the supply as available. It can only be fed by another tank which is sighted higher.

[buildersmate]

I don't agree. CH header tanks are invariably fed using a ball-valve type system to limit the flow to a maximum level in the header. A feed pipe put into such a ball valve will not operate unless there is decent mains pressure. You'd need a minimum of a 8m head of water to stand any chance of the valve working - unless you can devise another method of controlling it.

[Canary42]

Thank you for your answers - I'll go for the mains solution to be safe since I'll only have about 1.5 metres head from the cold water tank.