DIY Doctor

How to measure water pressure?

Postby massi » Mon Mar 08, 2010 10:22 am

I would like to install, a shower mixer on the bath as my still has to separeta ones for hot and cold and no shower in the bath.
I have been looking around and most of those on the market are at least 1 bar pressure minimum requirements.

I know that because I have a combi boiler the pressure should autiomatically assumed to be around 1 bar.
Even though, I can see that the water flow from the hot water tap on the bath it is not at is greatest. Is there a way or a tool to measure what is the pressure coming to that tap or I mean would that be the same to al taps anyway?

The needle on the pressure meter gauge of the combi boiler is set always at 1,5 bar. Would that be the place to look for the overall water pressure or is somewhere completely different?
Thanks for your attention
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Postby plumbbob » Wed Mar 10, 2010 10:22 pm

The pressure reading on the combi that you say is 1.5 bar has absolutely nothing to do with the hot water pressure which will almost certainly be much more. The reading is there to show the pressure in the heating circuit and is set manually by a filling loop.

If you have a combi, the water pressure is mains fed and could be as high as 5 bar. Whatever, it should be sufficient to supply a mixer shower.

Now the only word of caution is not to do with pressure, but flow rates. Clogged water mains or old/small combis cannot supply enough hot water to make the shower work satisfactorily. Test this by timing how long it takes to fill a fizzy drink bottle for example, then compare that to the flow rate of the shower you would like to fit.
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Postby htg engineer » Thu Mar 11, 2010 7:33 pm

As plumbbob says, it's the flow rate that's important - litres per minute.

If your shower says you need a certain pressure for it to work, you can buy a pressure gauge from screwfix that screws directly onto a washing machine valve.

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