Hi,

I have pretty low mains water pressure (just over 1 bar) and a fairly
low flow rate to the taps. Thames Water won't do anything because they
say it is within acceptable limits. I've just been looking at these
things:
http://www.machinemart.co.uk/product...5&g=122&r=2158
It would be an easy job to put one into the incoming main in the
cellar, but would it make any worthwhile difference. Rate of flow is
more important to me than pressure, especially when more than one tap
is open. I've never quite got my head around the difference between
rate of flow and pressure, but I don't see how one of these things
could actually suck more water out of the incoming supply in order to
increase the rate of flow.

On Mon, 15 May 2006 10:41:07 -0700, Martin Pentreath wrote:

Hi,

I have pretty low mains water pressure (just over 1 bar) and a fairly
low flow rate to the taps. Thames Water won't do anything because they
say it is within acceptable limits. I've just been looking at these
things:
http://www.machinemart.co.uk/product...5&g=122&r=2158
It would be an easy job to put one into the incoming main in the
cellar, but would it make any worthwhile difference. Rate of flow is
more important to me than pressure, especially when more than one tap
is open. I've never quite got my head around the difference between
rate of flow and pressure, but I don't see how one of these things
could actually suck more water out of the incoming supply in order to
increase the rate of flow.

It is illegal to pump water out of the mains without a permit (which
likely won't be given).

There are three ways to improve the mains water to your home. None cheap
all with drawbacks.

1) Replace the existing mains from the road with 25mm MPDE this will not
increase the standing pressure but will increase the flow rate.

2) Fit accumulators and a non-return valve. This only help if the
pressure is good during most/some of the day and not at other times when

3) Apart from the sink put all water into a storage cistern as low as
possible and then fit a quality negative head pump to supply all the rest
of the house.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

"Martin Pentreath" wrote in message
oups.com...
Hi,

I have pretty low mains water pressure (just over 1 bar) and a fairly
low flow rate to the taps. Thames Water won't do anything because they
say it is within acceptable limits. I've just been looking at these
things:
http://www.machinemart.co.uk/product...5&g=122&r=2158
It would be an easy job to put one into the incoming main in the
cellar, but would it make any worthwhile difference. Rate of flow is
more important to me than pressure, especially when more than one tap
is open. I've never quite got my head around the difference between
rate of flow and pressure, but I don't see how one of these things
could actually suck more water out of the incoming supply in order to
increase the rate of flow.

It's illegal to pump water out of the mains supply, this is so dirty water
does not get sucked in the leaking pipes.

You can however, pump water from a tank, so, if you have a tank in the loft,
you can stick a pump on the outlet from this (and the hot water cylinder, if
you have one)

Pressure is the force the water is trying to get out of the pipe, so with
everything off, the pipes and taps are holding back 1 bar of pressure, 1 bar
is like having a tank of water 10 meters high, so if you had a 15mm pipe
connected to a tank of water 10 meters in the air, the pressure would be
about 1 bar, however, if you had 22mm pipe connected, the pressure will be
the same, but the flow will be greater. 10mm pipe will still be 1 bar, but
the flow will be far less.

Have you made sure all you stopcocks are fully open?
If you have any of the silver service valves
(http://www.screwfix.com/app/sfd/cat/...29674&id=17447 or
http://tinyurl.com/mcdg7
these will reduce the flow quite a lot, as the hole in the moving ball is
only about 10mm
Your main stopcock may also be restricting the flow.

If it is causing you a big problem, I would do the following...

time how long it takes to fill a bucket from your kitchen tap, and also your
outside tap (if you have one)

Turn off the water at the stopcock
Disconnect the pipe to the rest of the house
connect a piece of pipe (plastic would be best here)
do the test again here, if there is no significant improvement, it may be
the stopcock

If this is the case, then turn the water off in the road
remove the stop cock and repeat the test - if again there is no significant
improvement, then you are stuffed!


Sparks...

I would suggest in line with the other answers that the problem lies
more in the piping than the pressure. If the pipes are small and have
restrictions then higher pressure will overcome that but actually 1 bar
pressure with adequate piping is quite reasonable. The reason for
saying that is the flow from my hot water taps is perfectly acceptable
with all running despite having a head of less than 5 metres - ie 0.5
bar - but I recognised I had a potential problem when I replumbed and
used 22mm pipe with long bends and full bore isolators, and a 28mm feed
to the hw tank.

The thing of course id that the pressure being measured by the water
board is the static pressure - ie without any water flowing !

Rob

Ed - Can I ask what a 'negative head pump ' pump is please ?

Rob

On Tue, 16 May 2006 02:40:59 -0700, robgraham wrote:

Ed - Can I ask what a 'negative head pump ' pump is please ?

Essentially a pump which with a non-return valve and a pressure switch so
that it switches on when the pressure in the outlet pipe fails below a
certain amount (in theory when water is been drawn off).
There is also a small expansion vessel to prevent 'hunting'.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards