Water Pressure.

[trigger01]

Hi, Hoping someone can give me a quick bit of advice.
We are having an extension and we haven't lived at the house previously. As part of the extension, the gravity-fed water system has been removed and we are due to have a combi boiler instead. I am a little worried about the water pressure and have asked the plumber a few times about it but not gotten much feedback.
Currently, only the outside tap and the utility tap are connected and all other pipework has been ripped out and replaced. The two taps are basically on the oposite side of the wall to each other so literally a couple of feet apart.
Inside the house, it takes 7.4 seconds to fill a litre jug. Outside it takes 5 seconds.
So it would seem pressure to the house is ok but not internally. What should I be telling the plumber to do? I know this seems a bit back to front but I am not getting much of a response from him.

 

[opps]

10 to 15L per min is considered to be "good".

7.4 seconds to fill one litre equates to 8L per min.

5 seconds is 12L per min

BTW, I am not a plumber.

 

[jacko555]

Is the stop tap fully opened?

 

[terryplumb]

The utility tap may have restrictive hoses ,is it a monobloc ?

 

[trigger01]

Thanks guys, yeah I was hoping it would be at least 10l per min as that seems to be the recommended minimum.
Stop tap looks fully open and yes its a mixer tap. There are bathroom taps that arent plumbed in at the moment but they also seemed slow before the build and again both are monobloc type.

 

[oldbuffer]

1. There are two factors involved in determining whether or not a combi boiler is suitable:
1a. Flow rate which you have measured and appears to be around 10 litres / minute (lpm)
1b. Pressure, which requires a gauge to measure and has two facets:
1bi. Static pressure, which is the pressure measured with no water running.
1bii. Dynamic pressure, measured with a mains fed tap running.
2. The water in a shower is a mixture of hot and cold. A rough rule of thumb is that you need 1/3rd cold and 2/3rds hot water for a comfortable shower. Obviously depends on the temperature you want, the incoming cold temperature and the hot water temperature output from the boiler so pretty variable.
3. Your 10 lpm input is the maximum you will get out of any appliance, PROVIDED it is the only appliance open. This is not going to support a drench type shower, and is about double what you might get out of an electric shower.
4. I would suggest you need:
4a. A minimum 15 lpm.
4b. A minimum dynamic pressure of around 2.0 bar.
5. Don't forget that you are unlikely to get two showers running simultaneously on a combi.
6. The plumber should have measured the pressure and flow rate before considering a combi.