"TMC" wrote in message
...

"MuddyMike" wrote in message
om...

"TMC" wrote in message
...

"Alan (BigAl)" wrote in message
...
Am I right in saying that with a combination boiler with no header
tank, with direct connection to the mains water, that is is
inappropriate to use a booster pump?

I am planning to redo the bathroom, to include a separate shower unit.
I was planning to use a thermostatic controlled shower unit to blend
hot and cold feeds.

Presently we have a shower over the bath, with a combined tap/shower
without any temperature regulation.
This is very hard to adjust and both the hot and cold flows seem to be
quite restricted. However, the old tap/shower unit may well have got a
bit of scale or gunge, but I was expecting more vigorous flow, and
suspected that the low pressure might be detrimental with a new shower
too.

I just did a pressure test, and have 32 psi dead ended pressure.
This was on the ground floor, so 3 metres higher (bathroom upstairs) it
will be ~5 psi lower.

That seems a bit lower than I expected, but I have no real data to
compare it with.

Checking the installation instructions from a shower plucked at random
from 'tinterweb, it seems that it would be ok with pressures of 1 bar,
or even lower if the flow restrictors are removed.

Am I worrying needlessly? Am I missing something? Does anyone have any
advice for me please?



Cheers Alan
I am sure there will be an expert along soon

but in the meantime

for a combi boiler system use a pressure balanced mixer

traditional showers have a temperature balanced mixer which needs the
incoming supply of both hot and cold to be the same pressure the cold
feed would come from the output of the header tank for the hot water
system not from the incoming mains


I am confused, I thought combi boilers did away with the loft tank? Don't
both hot and cold come at mains pressure?

Mike
the pressure to the boiler for the hot water is mains pressure in thbut
the output of the boiler is limited to the heating potential of the boiler

The flow may be restricted but surely the pressure is the same?

Mike