Water pressure and accumulators
 

I'm still looking for a way of improving my water pressure and rate of
flow (barely over 1 bar and 11 litres per minute).

Thames water have given me a price of £1400 to replace the furred-up
0.5" lead communication pipe from the main in the street to the
boundary of my land with 32mm MDPE. This could be the ideal lasting
solution, although there is no guarantee that the pressure in the main
in the street is that great, so I can't be sure that the rate of flow
would be increased all that dramatically.

My plumber has suggested putting an accumulator in the cellar as an
alternative. I've googled for information on these things, but I don't
seem to be able to find anything very useful. My understanding is that
an accumulator is a large cylindrical tank fed from the main with a
pump which pressurises it so that everything fed from the accumulator
is at decent pressure, is that right? Does anyone have any experience
of these things? The plumber reckons that it would cost about £500 to
install. I'm tempted to go ahead with this, but I'm a bit put off by
the idea of a noisy pump whirring away underneath the living room
floor every time anyone opens a tap.

Thames water have given me a price of £1400 to replace the furred-up
0.5" lead communication pipe from the main in the street to the
boundary of my land with 32mm MDPE. This could be the ideal lasting
solution, although there is no guarantee that the pressure in the main
in the street is that great, so I can't be sure that the rate of flow
would be increased all that dramatically.

Measure the static pressure of your system over time when you aren't drawing
water. This will give you some idea of how the main is responding to demands
of other nearby users. If it stays consistent and at a reasonable value
(over 1 bar), then provided there are plenty of other users on the same main
to make it a good test, it suggests that plenty of water is available, if
you can install a large enough pipe to tap it. If the pressure often drops
below 1 bar (especially during morning shower rush), it suggests that the
main really isn't up to the job. When taking measurements, ensure that no
water is being drawn, such as by a loft tank or toilet cistern.

Christian.

In an earlier contribution to this discussion,
Martin Pentreath wrote:

I'm still looking for a way of improving my water pressure and rate of
flow (barely over 1 bar and 11 litres per minute).

Thames water have given me a price of £1400 to replace the furred-up
0.5" lead communication pipe from the main in the street to the
boundary of my land with 32mm MDPE. This could be the ideal lasting
solution, although there is no guarantee that the pressure in the main
in the street is that great, so I can't be sure that the rate of flow
would be increased all that dramatically.

My plumber has suggested putting an accumulator in the cellar as an
alternative. I've googled for information on these things, but I don't
seem to be able to find anything very useful. My understanding is that
an accumulator is a large cylindrical tank fed from the main with a
pump which pressurises it so that everything fed from the accumulator
is at decent pressure, is that right? Does anyone have any experience
of these things? The plumber reckons that it would cost about £500 to
install. I'm tempted to go ahead with this, but I'm a bit put off by
the idea of a noisy pump whirring away underneath the living room
floor every time anyone opens a tap.

If there's plenty or static pressure, but a poor flow due to a restricted
supply pipe, I wonder whether you would need a pump if you were to use an
accumulator. I admit that I don't have any experience of these things, but
if you had a large sealed (pressure capable) tank fed from the mains through
a non-return valve, and connected to a pressure vessel similar to the type
used on sealed heating systems, but much larger, you should be able to
satisfy short duration high flow demands from this - and it would re-charge
itself at its leisure. Depending on the actual static pressure in the mains,
you may need some device to cut the mains feed off when the accumulator
pressure reaches a specified value - but that doesn't sound to me like
rocket science!

Anyone know whether such systems exist?
--
Cheers,
Set Square
______
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Martin Pentreath wrote:

I'm still looking for a way of improving my water pressure and
rate of
flow (barely over 1 bar and 11 litres per minute).

Thames water have given me a price of £1400 to replace the
furred-up
0.5" lead communication pipe from the main in the street to the
boundary of my land with 32mm MDPE. This could be the ideal
lasting
solution, although there is no guarantee that the pressure in the
main
in the street is that great, so I can't be sure that the rate of
flow
would be increased all that dramatically.

My plumber has suggested putting an accumulator in the cellar as
an
alternative. I've googled for information on these things, but I
don't
seem to be able to find anything very useful. My understanding is
that
an accumulator is a large cylindrical tank fed from the main with
a
pump which pressurises it so that everything fed from the
accumulator
is at decent pressure, is that right? Does anyone have any
experience
of these things? The plumber reckons that it would cost about £500
to
install. I'm tempted to go ahead with this, but I'm a bit put off
by
the idea of a noisy pump whirring away underneath the living room
floor every time anyone opens a tap.

If there's plenty or static pressure, but a poor flow due to a
restricted
supply pipe, I wonder whether you would need a pump if you were to
use an
accumulator. I admit that I don't have any experience of these
things, but
if you had a large sealed (pressure capable) tank fed from the mains
through
a non-return valve, and connected to a pressure vessel similar to
the type
used on sealed heating systems, but much larger, you should be able
to
satisfy short duration high flow demands from this - and it would
re-charge
itself at its leisure. Depending on the actual static pressure in
the mains,
you may need some device to cut the mains feed off when the
accumulator
pressure reaches a specified value - but that doesn't sound to me
like
rocket science!

Anyone know whether such systems exist?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.



Pumps and accumulators sound complicated and liable to fail in the
future.

I don't know how long your 1/2" lead pipe is, but if we are talking of
a normal front garden senario, digging a trench and laying the blue
MDPE is a fairly straightforwards job. The pipe is dead cheap and easy
to terminate. A navvy for a day (perhaps £100) and maybe another £100
for the pipe and fittings. When I had to do this at my last house I
dug the trench myself before going to work and left a plumber to do
the connection. Now (a few years later !) I'd do it the other way
round. I had to pay the local council a 'disturbance fee' to make good
the pavement but it wasn't very much.

You may well be able to 'mole' the pipe without digging a trench (a
pit is dug at both ends and a special air operated device rams it's
way from one to the other dragging the pipe behind it). Specialist
conntractors and Hire Shops have them

AWEM

Martin Pentreath wrote:

Thames water have given me a price of =A31400 to replace the furred-up
0.5" lead communication pipe from the main in the street to the
boundary of my land with 32mm MDPE.

I believe that, if you have replaced the lead water pipe on your
property, then the water supplier 'can be required' to replace
their lead service pipe. I got this from the OFWAT website. I think
this was a government initiative from a few years back. I was unable
to find any details about how one would 'require' the supplier to
replace their lead pipes, or who would do the requiring. Even if they
did replace the lead service pipe, they may still want a wad of cash to
upgrade it from say 20mm to 32mm. If anyone's got more info, I'd be
grateful to have it.

I'd also check your neighbours' water pressures, it may be a
damaged pipe or fitting on your supply.


My plumber has suggested putting an accumulator...

My understanding is that accumulators will remedy low flow rate (i.e.,
restricted pipe ) but not low static pressure. An accumulator is the
big brother of the bladder expansion vessels, most commonly seen on
sealed heating systems. They have a volume of 100, 150+ litres, as
against 6 or 12 on most domestic heating systems. The water
accumulates in the bottom of the vessel, at a low flow rate but over a
long time, compressing the gas charge in the top. On opening a tap, you
get the benefit of the additional flow rate propelled by the
accumulator's gas charge until the accumulator pressure has dropped
to equal the mains pressure (which will have dropped, because of the
draw off). The flow rate diminishes as the gas expands.

A pumped system can remedy both low pressure and low flow rates, but
you have to have a storage cistern or break tank on the mains, upstream
of the pump. Do a Google for pressurisation units (or pressurization
units for those who are Yanks, pedantic and/or correct). The pump draws
water from the tank and is switched by a pressure switch. There's
usually an accumulator/ bladder vessel downstream of the pump, to
reduce the number of on/off cycles caused by small volume draw-offs.

On Mon, 17 Jan 2005 04:53:28 -0800, Martin Pentreath wrote:

I'm still looking for a way of improving my water pressure and rate of
flow (barely over 1 bar and 11 litres per minute).

Thames water have given me a price of £1400 to replace the furred-up
0.5" lead communication pipe from the main in the street to the
boundary of my land with 32mm MDPE. This could be the ideal lasting
solution, although there is no guarantee that the pressure in the main
in the street is that great, so I can't be sure that the rate of flow
would be increased all that dramatically.

My plumber has suggested putting an accumulator in the cellar as an
alternative. I've googled for information on these things, but I don't
seem to be able to find anything very useful. My understanding is that
an accumulator is a large cylindrical tank fed from the main with a
pump which pressurises it so that everything fed from the accumulator
is at decent pressure, is that right? Does anyone have any experience
of these things? The plumber reckons that it would cost about £500 to
install. I'm tempted to go ahead with this, but I'm a bit put off by
the idea of a noisy pump whirring away underneath the living room
floor every time anyone opens a tap.

Accumulators solve the problem when the pressure is OK sometimes and bad
at others (like at 7am when everyone is running a shower).
They do not have pumps. AFAIK

If the pressure in the main is over 1 bar 32MDPE will be a very good flow.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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