In an earlier contribution to this discussion,
kipper wrote:

I have a gravity fed hot water system. Until recently it had a healthy
system presssure. No changes have been made to the system and no
recent work has been carried out. Pressure has dropped off to the
point where it can take 20 minutes to run a bath. There has been a
corresponding drop (although not quite as significant) in cold water
presure. Pressure starts good and tails off as if a down pipe were
emptying but not being backed up.

All valves feeding the header tanks seem to be open and depressing the
ballcocks results in appropriate water flow into the tanks.

You've got either a blockage or an air-lock in the pipes. Does this happen
with all hot taps, or only on the bath? Does the cold water for the bath
also come from the header tank, or direct from the mains?

The standard cure is to backflush the pipework with mains pressure. If the
bath cold supply is mains, you need to connect hot and cold taps together,
and turn them both on - hot first. This will get rid of any air lock and
push any blockage back into the header tank. Only turn on the cold tap
gently until you're sure that water is flowing back into the header. If
there's a solid blockage, you could get full mains pressure in the hot water
cylinder with undesirable consequences!

If the bath tap cold supply comes from the header, you'll need to find a
mains cold supply somewhere else (kitchen tap?) and use a hosepipe to
connect it to the bath tap. In this case, you'll need to back-flush both hot
and cold bath taps.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.