On Tue, 12 Jul 2011 14:10:13 +0100, "Alan \(BigAl\)"
wrote:

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

Before installing a shower in my son's bathroom a couple of years ago
(albeit one over a bath) I lashed up a connection using garden hose
between the hot water feed from the combi and his new shower head,
temporarily fixed at roughly the finished height with bucket
underneath, just to check the flow/pressure. It seemed ok.

Final installation had hot and cold feed into a thermostatic mixer,
thence to normal shower head on flexible hose. Still working ok and no
problems with other taps being turned on/off.

As said above, don't expect a waterfall shower through a combi!