I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min from the
cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating the
water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as the
input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold water
tank in the loft.

5) Any others?

In an earlier contribution to this discussion,
Andrew Beck wrote:

I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains
water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min
from the cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating
the water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as
the input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water tank in the loft.

5) Any others?



As I see it, there are only 2 options:

A) Sort out the cold supply to the house, or

B) Throw out the combi, and revert to a stored hot water system

[There are some rules of thumb for cold flow rates needed to sustain mains
pressure hot water systems. I can't remember exactly what they are - but I'm
sure that they're closer to 30 litres/min than to 10! Whoever fitted a combi
clearly shouldn't have done so without first sorting out the cold supply].

Cheers,
Set Square
--
Please reply to newsgroup. Reply address is invalid.

It was British Gas that fitted the Combi for the previous owner.

The boilers manual says minimum flow rate for the boiler is 2.7 l/min
The mains water pressure for maximum flow rate is 0.8 bar

I know the pressure of the mains above 2.5 bar (as it can fill the closed
heating circuit to this pressure)

Andrew

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Andrew Beck wrote:

I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains
water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min
from the cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating
the water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as
the input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water tank in the loft.

5) Any others?



As I see it, there are only 2 options:

A) Sort out the cold supply to the house, or

B) Throw out the combi, and revert to a stored hot water system

[There are some rules of thumb for cold flow rates needed to sustain mains
pressure hot water systems. I can't remember exactly what they are - but
I'm
sure that they're closer to 30 litres/min than to 10! Whoever fitted a
combi
clearly shouldn't have done so without first sorting out the cold supply].

Cheers,
Set Square
--
Please reply to newsgroup. Reply address is invalid.

In an earlier contribution to this discussion,
Andrew Beck wrote:

It was British Gas that fitted the Combi for the previous owner.

The boilers manual says minimum flow rate for the boiler is 2.7 l/min
The mains water pressure for maximum flow rate is 0.8 bar

I know the pressure of the mains above 2.5 bar (as it can fill the
closed heating circuit to this pressure)

Andrew


Yes, but I fear that you're confusing static pressure with pressure when
there's a significant flow. From what you said earlier, the flow to the
combi more or less stops when you turn cold taps on. This indicates that,
when water is flowing elsewhere, the pressure drops to a level which is
insufficient for the combi - presumably to below the required 0.8 bar. This
is almost certainly because of restrictions in the supply line - which will
cause a pressure drop which is dependent on flow rate.

To illustrate with a guesstimate example: Attach pressure gauge to pipework
just above the stop-cock. Static pressure, with all taps off: 2.6 bar. Turn
kitcken tap full on - giving 10 litres per minute, or whatever. Pressure now
0.6 bar - because a flow of 10 litres per minute causes a pressure drop of
2.0 bar down your 15mm supply pipe. [These aren't the actual figures, of
course - but I have a shrewd suspicion that they ain't that far out].
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

You are right, this is static pressure.

The boiler spec says it requires a pressure of 0.3 bar for minimum flow rate
(2.7 l/min)

Interesting I have found the following quote about water flow rate on my
water company's web site

" A simple check: provided the cold tap in your kitchen (whilst running at
full bore) can almost fill a 2 gallon bucket within about 1min, your flow
and pressure is satisfactory. "
(http://www.threevalleyswater.co.uk/h...pressure.shtml)

Which is about what I'm getting.
My problem is an unbalanced flow, all cold and no hot.

What I'm looking for is a balanced flow i.e. the cold water flow is no more
than 50 % of the total water flow.

Andrew


"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Andrew Beck wrote:

It was British Gas that fitted the Combi for the previous owner.

The boilers manual says minimum flow rate for the boiler is 2.7 l/min
The mains water pressure for maximum flow rate is 0.8 bar

I know the pressure of the mains above 2.5 bar (as it can fill the
closed heating circuit to this pressure)

Andrew


Yes, but I fear that you're confusing static pressure with pressure when
there's a significant flow. From what you said earlier, the flow to the
combi more or less stops when you turn cold taps on. This indicates that,
when water is flowing elsewhere, the pressure drops to a level which is
insufficient for the combi - presumably to below the required 0.8 bar.
This
is almost certainly because of restrictions in the supply line - which
will
cause a pressure drop which is dependent on flow rate.

To illustrate with a guesstimate example: Attach pressure gauge to
pipework
just above the stop-cock. Static pressure, with all taps off: 2.6 bar.
Turn
kitcken tap full on - giving 10 litres per minute, or whatever. Pressure
now
0.6 bar - because a flow of 10 litres per minute causes a pressure drop of
2.0 bar down your 15mm supply pipe. [These aren't the actual figures, of
course - but I have a shrewd suspicion that they ain't that far out].
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Fri, 3 Sep 2004 22:30:27 +0100, "Andrew Beck"
wrote:

You are right, this is static pressure.

The boiler spec says it requires a pressure of 0.3 bar for minimum flow rate
(2.7 l/min)

Interesting I have found the following quote about water flow rate on my
water company's web site

" A simple check: provided the cold tap in your kitchen (whilst running at
full bore) can almost fill a 2 gallon bucket within about 1min, your flow
and pressure is satisfactory. "
(http://www.threevalleyswater.co.uk/h...pressure.shtml)

Which is about what I'm getting.

They would say that.

This works out to slightly over 9 litres per minute.

The statutory minimum for water companies to meet is.. you'll never
guess.... 9 litres per minute,

Of course it isn't satisfactory - a more reasonable figure is twice
that. The trouble is that in some places the water companies would
have to spend a fortune to meet 20 lpm.


My problem is an unbalanced flow, all cold and no hot.

What I'm looking for is a balanced flow i.e. the cold water flow is no more
than 50 % of the total water flow.

You could try a simple solution of introducing a restricting valve on
the cold path to force more flow through the hot path; or perhaps a
pressure equalising valve. The trouble is that you haven't got much
to work with.

The best solution would be to look into getting the supply from the
street upgraded.

Failing that, another solution would be to install a conventional hot
water cylinder with a storage tank in the roof and fill that from the
mains. Heat this cylinder from the heating circuit by adding a
divertor valve and cylinder thermostat. Use the stored hot water for
baths and showers and the combi for less critical applicatiions like
the kitchen.



..andy

To email, substitute .nospam with .gl

In an earlier contribution to this discussion,
Andrew Beck wrote:

My problem is an unbalanced flow, all cold and no hot.

What I'm looking for is a balanced flow i.e. the cold water flow is
no more than 50 % of the total water flow.

Presumably the combi works ok on just hot - but stops working when you turn
on a cold tap?

Water will always take the line of least resistance. It is fair to assume
that the path through the boiler presents more resistance than the path to
an open cold tap. What happens if you partially close the cold tap and
reduce it to a trickle, does the hot pick up again? If so, you can probably
get a *balance* by adjusting the cold tap - but you still might not get an
acceptable *total* (i.e. hot + cold) flow rate if the basic cold supply is
inadequate.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"Andrew Beck" wrote in message
. ..
I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min from
the
cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating the
water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as the
input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water
tank in the loft.

5) Any others?

Check the flowrate at the kitchen tap.
Replace the stop cock with full bore version.

Check again.

If still bad, replace the water main back to the street.

On Wed, 1 Sep 2004 23:47:34 +0100, "IMM" wrote:


"Andrew Beck" wrote in message
...
I think my house has a water flow rate problem and I'm looking for a
solution.



2) replace the cold water supply pipe to the main pipe in the road as the
input in to the house is only 15mm
Not really an option.



Check the flowrate at the kitchen tap.
Replace the stop cock with full bore version.

Check again.

If still bad, replace the water main back to the street.


See (2).



..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Wed, 1 Sep 2004 23:47:34 +0100, "IMM" wrote:


"Andrew Beck" wrote in message
...
I think my house has a water flow rate problem and I'm looking for a
solution.

2) replace the cold water supply pipe to the main pipe in the road as
the
input in to the house is only 15mm
Not really an option.


Check the flowrate at the kitchen tap.
Replace the stop cock with full bore version.

Check again.

If still bad, replace the water main back to the street.


See (2).

It must be made an option.

On Thu, 2 Sep 2004 00:34:41 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Wed, 1 Sep 2004 23:47:34 +0100, "IMM" wrote:


"Andrew Beck" wrote in message
...
I think my house has a water flow rate problem and I'm looking for a
solution.

2) replace the cold water supply pipe to the main pipe in the road as
the
input in to the house is only 15mm
Not really an option.


Check the flowrate at the kitchen tap.
Replace the stop cock with full bore version.

Check again.

If still bad, replace the water main back to the street.


See (2).

It must be made an option.

Sigh....


..andy

To email, substitute .nospam with .gl

A friend of mine had to have your option 2 done (22mm new supply pipe
fitted) when he got a combi boiler fitted as the flow rate into the house
was not high enough. House previously had no cerntral heating, just a tank
in the loft feeding cold taps and immersion heated hot water tank.

Also had to have quite a bit of internal plumbing re-arranged so that no
matter what was happening with the cold taps sufficient flow was left for
hot water.

Anyway the lodgers he had hated it as it took ages to fill the bath compared
to the tank and immersion heater. Mind you they now had heating !!!

"Andrew Beck" wrote in message
. ..
I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min from
the cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating the
water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as the
input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water tank in the loft.

5) Any others?

"Andrew Beck" wrote in
:

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as
the input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water tank in the loft.

I think option 3 and 4 have a chance.

I may be talking rubbish, but I think a pumped supply from a reservoir
tank would help.

Perhaps if you ran the cold off the main, and the combi off the tank
with a pump, you would get a result.

My only experience(!!) is only running a pumped electric shower off the
cold tank because of crosstalk between the shower, bog cistern, cold
taps etc.

This has provided a perfectly buffered feed, and on a larger scale might
suit you.

You would need a suffieciently beefy pump (not a problem, I think) and
be sure the cold tank is big enough to take up the slack while the combi
is in use, perhaps lots of baths would require a big tank.

mike

"Andrew Beck" wrote in message
. ..
I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min from
the
cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating the
water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as the
input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water
tank in the loft.

5) Any others?

Fit an accumulator, then no pumps and high pressure showers all around.
http://www.gah.co.uk/

On Wed, 01 Sep 2004 22:33:23 +0100, Andrew Beck wrote:

I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min from the
cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating the
water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as the
input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold water
tank in the loft.

5) Any others?

Before deciding what to do I would want to work out what the problem with
the mains is.

If the standing pressure is low then some sort of storage tank/pump will
be needed, or even reverting to a conventional system (no need to throw
the boiler out - just add the HW cisterns and cylinders).

If the standing pressure is 2bar+ then the problem really is the supply
and/or internal pipework.

You just might find that there is a stack of crap stuck in the mains pipe
work somewhere (on the stop cock most likely) whose removal will fix a lot
of things.

--
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

"Ed Sirett" wrote in message
news
On Wed, 01 Sep 2004 22:33:23 +0100, Andrew Beck wrote:

I think my house has a water flow rate problem and I'm looking for a
solution.

The house has a combi boiler and everything is run off the mains water.

The water flow rate from a single cold tap upstairs is about 10 l/min
The water flow rate from a single hot tap upstairs is about 8 l/min

The difference is probably due to the resistance of the combi boiler.

The problem is that if you turn on a cold tap the hot water flow rate
reduces.
If you turn on a hot and cold tap the flow rate is about 9.5 l/min from
the
cold and about 0.5 l/min from the hot.
The low flow rate of the hot causes the combi boiler to stop heating the
water due to inefficient flow rate.

Solution Ideas, will the work?

1) A pressure equalisation valve on the hot and cold water supplies?

2) replace the cold water supply pipe to the main pipe in the road as
the
input in to the house is only 15mm
Not really an option.

3) run the cold of a tank in the loft that is pumped?

4) run the cold and combi of a tank in the loft that is pumped?
Before the combi was installed by the previous owner there was a cold
water
tank in the loft.

5) Any others?

Before deciding what to do I would want to work out what the problem with
the mains is.

If the standing pressure is low then some sort of storage tank/pump will
be needed, or even reverting to a conventional system (no need to throw
the boiler out - just add the HW cisterns and cylinders).

If the standing pressure is 2bar+ then the problem really is the supply
and/or internal pipework.

You just might find that there is a stack of crap stuck in the mains pipe
work somewhere (on the stop cock most likely) whose removal will fix a lot
of things.

On a poor performing old mains pipe I once removed the house stop cock and
replaced it with a full bore one. I thought there might be a bock age in
the line, so inserted a large bore hose pipe on the new full bore stop cock.
Lead the hose to the garden and tuned on the water at the street. The crap
that came out !! I never measured it, however the water pressure was
excellent after.