Dynamic pressure equals static pressure

You need to see what the reducing valve is actually supplying!

It does not seem to be supplying the shower based on that!

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You need to see what the reducing valve is actually supplying!

It does not seem to be supplying the shower based on that!


Tony, as far as I can tell that pipe is where the cold mains comes up into the house. (hence it has the main shut off stop cock)

Doesn't that mean everything (inc the showers) are fed from this pipe??

You may want to look up 'pump curves'. These go from
zero flow rate at some max pressure
max flow rate at some pressure.

It's almost certainly not a straight line.

Absent a PRV which will artificially level or even overcompensate the max pressure allowed, whatever you get delivered to your house will somewhere along the line for your particular water supply.

IIRC, 2 to 5 feet per second is a desirable flow rate.

If you are more comfortable with electrical circuits a suitable analog for pressure would be voltage and for flow rate, current.
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I decided not to remove the grey cap and measure from there, but I did turn the prv to 5 bar and measure from the garden tap.

It read 4.8bar static and 4.8bar again when the kitchen tap was on full blast.

If my pressure is this good why do I find the water delivery at a shower tails off so much when I open another outlet?

With no pumps how is the system pressurized? Large elevated tanks?
The utility company has to provide a certain pressure and performance, often they give more.

My house has 7bar incoming mains pressure.

In London it can vary from 1bar to 9 depending.

Remember over here we have utilities and houses older than your country.

My dad's house is 450 years old give or take.
I think i mentioned in another thread that those taps are not the best for measuring the potential of the system.

Thanks Dan.

I didn't take the grey cap off because it didn't look like my gauge would fit on to that outlet (but I could be wrong)

I will try and measure from there later on today.

However, assuming I've got at least 5 bar dynamic pressure (max setting on prv) why do I get this fall off in water delivery when two outlets are open?

Thanks Dan

The incoming mains is 22mm and as far as I know the pipework is then 22mm throughout the house with 15mm tapped off to supply the showers.

Is there a logical way to figure out where this restriction is? Could it be that the 22mm inlet pipe itself is not man enough for the job?
Dan has already pointed out that your garden tap probably has a non return valve so whatever pressure it reads it will stay at that figure !

There is a way round this! Close your stopcock, turn on kitchen tap and then fit your gauge. THEN turn on the stopcock!

But far better to get the 6 Bar 1/4" gauge and it can stay permanently on the PRV.

The PRV might have some debris lodged on the inlet side! While the stopcock is off you could remove it and look up the inlet port!

Or you could have a restricted mains feed or even the garden/street valves may not be fully open!

Thanks DIO, I'll order one today.

I tried Tony's trick and the garden tap gauge still shows a rock steady 2.8bar even with the kitchen tap fully open.

I also did some other measurements today of flow rates (at the garden tap)

1) At 3 bar its 19l/min

2) At 4 bar its 24l/miin

3) At 5 bar its 26l/min

4) At 6 bar its 28l/min

The question I'm really trying to get to the bottom off is whether it's worth me upgrading my inlet pipe to something larger than 22mm


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