"Paul Worsley" wrote in message
.. .
"Noddy's Big Ears" wrote in message
...
Hi all

I have a particular problem with hot water in my house. The details
are as follows:



SNIP


What is happening is that when you use a tap downstairs, it is creating a
vacuum in the supply pipe to the 2nd storey. This is due to not enough
head of water supplying the cylinder.

I interpreted the OPs system as having a loft higher than the 2nd floor
taps. The problems arose when a downstairs tap is turned on and otherwise
the 2nd floor taps delivered water at a low rate. Your interpretation may
differ?

You may find that the outlet in the top of the cylinder is constrained due
to a build up of lime scale, you can check this by removing the pipe and
looking into the fitting and pipe. Alternatively, the inlet to the tank is
constrained due to the bottom of the cylinder being full of limescale,
this is not so easy to check.

Agreed. Also worth considering is the size of the pipe from loft storage
tank into the cylinder.

If you are in a hard water area, and the tank is more than 15 years old,
the best thing might be to change it. If you do decide to change it,
consider an unvented mains fed cylinder - this would solve all your
problems.

Possibly but they are not a panacea. Also as an unvented cylinder has the
potential to explode if not installed correctly I would be wary of
suggesting someone who has to ask the original question undertakes this sort
of exercise

A normal pump is not going to help as you need to have a flow to start
with for the pump to cut in. You could use a negative head pump, but these
cost a fortune.

If there is a small flow then a negative head pump is not required. A
standard one will suffice.