"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

A pressure balanced shower assumes a constant hot water temperature which
one normally gets from a combi boiler and balances the differential in
pressure to get the required temperature

I have had a mira one fitted for 18 years without problem other than
replacing the shower head once and hose twice

I do not see how a booster pump can work with fixed volume output from the
boiler

Regards

Regards