Frank McGuire wrote:

It might sound a silly question, but -
If I connect a pressure gauge to the cold water tap in the kitchen sink and
turn the tap on full, will that give me a measure of the mains water
pressure?

It will, but that does not actually tell you much of use (other than you
have enough static pressure to exceed the minimum required by the boiler
(often 1 bar).

The kitchen is on the ground floor and fed directly from the mains.
(I don't want to spend ｣2000) on a combi boiler only to find it won't work!

You need to measure the flow rate, by timing how long it takes to fill a
container of known size from the fastest flowing tap in the house.

Under 10 lpm - no hope.
10 - 15 - too low unless you are fitting a low power combi (i.e. under
30kW) and will only even need one tap at a time

15-20 is better - but still not great. Over 20 is usually adequate.

A reasonable combi (say 35kW) will be able to manage about 15 lpm of
water at a usable temperature. So if the supply can manage 25 lpm that
should prevent the shower stopping when someone flushes the loo, or the
dishwasher decides to fill.

--
Cheers,

John.

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