The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.

However, once I had done that, I found that there was a horrific bang
every time I turned the tap off other than *very* slowly and gently. So,
at least as an interim solution, I closed the new valve down a bit - and
reduced the bang considerably. (That is, it would only happen when
really trying.)

Then I realised that the other water in the house that is fed directly
from the mains (one WC cistern and the cold water tank and CH
header/expansion) were also very prone to banging - which was new.

On to the next idea - when I had turned off the mains to do the job, had
I inadvertently turned it up higher when restoring water? Well - no. I
checked before turning it off - it was fully open - and back half a turn.

So I have now turned the under sink full bore valve full on and turned
the mains stopcock down. (Currently a bit too far - at about half-to-one
turn from fully closed.) Even at this setting the flow is pretty good.

As I had been working on the kitchen sink, there had been a couple of
vans and around half a dozen people on the main road nearby. They had
been staring at some water utility 'holes' - the covers of some were
open. The vans were marked with "PRV Maintenance" and a company name
(one of the outsource the work outfits that do most of the work for the
utilities - but I have forgotten which one). Looking up PRV I found only
one related meaning - Pressure Reducing Valve. Could they have done
something like turn up the pressure?

Make any sense to anyone?

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

"Rod" wrote in message
...
The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.

However, once I had done that, I found that there was a horrific bang
every time I turned the tap off other than *very* slowly and gently. So,
at least as an interim solution, I closed the new valve down a bit - and
reduced the bang considerably. (That is, it would only happen when really
trying.)

Then I realised that the other water in the house that is fed directly
from the mains (one WC cistern and the cold water tank and CH
header/expansion) were also very prone to banging - which was new.

On to the next idea - when I had turned off the mains to do the job, had I
inadvertently turned it up higher when restoring water? Well - no. I
checked before turning it off - it was fully open - and back half a turn.

So I have now turned the under sink full bore valve full on and turned the
mains stopcock down. (Currently a bit too far - at about half-to-one turn
from fully closed.) Even at this setting the flow is pretty good.

As I had been working on the kitchen sink, there had been a couple of vans
and around half a dozen people on the main road nearby. They had been
staring at some water utility 'holes' - the covers of some were open. The
vans were marked with "PRV Maintenance" and a company name (one of the
outsource the work outfits that do most of the work for the utilities -
but I have forgotten which one). Looking up PRV I found only one related
meaning - Pressure Reducing Valve. Could they have done something like
turn up the pressure?

Make any sense to anyone?


They may have been reducing the pressure as they have realised that this is
the cheapest way to meet government leak reduction targets (less pressure,
less water lost). They have a statutory minimum to maintain so pressure and
leak management programmes concentrate on tuning the supply systems down to
the statutory minimum. It is, of course, possible that subsequent to such a
tuning operation (or coincidentally), someone has complained that they are
not getting their statutory minimum or, just as likely, a new development
tacked on the end of the supply pipe is under pressure and the pressure has
been increased to compensate further back, leading to an overpressure in
your road.

As to your banging, this is generally caused by loose pipework whacking
something as it flexes under pressure step changes such as shutting off a
fast flow. One approach would be to get someone else to help and to try and
isolate where exactly the physical bang is coming from and the direct cause.
Whatever the incoming pressure (within normal limits) a domestic
installation should be possible without the banging!


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

"Rod" wrote in message
...
The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.

However, once I had done that, I found that there was a horrific bang
every time I turned the tap off other than *very* slowly and gently. So,
at least as an interim solution, I closed the new valve down a bit - and
reduced the bang considerably. (That is, it would only happen when really
trying.)

Then I realised that the other water in the house that is fed directly
from the mains (one WC cistern and the cold water tank and CH
header/expansion) were also very prone to banging - which was new.

On to the next idea - when I had turned off the mains to do the job, had I
inadvertently turned it up higher when restoring water? Well - no. I
checked before turning it off - it was fully open - and back half a turn.

So I have now turned the under sink full bore valve full on and turned the
mains stopcock down. (Currently a bit too far - at about half-to-one turn
from fully closed.) Even at this setting the flow is pretty good.

As I had been working on the kitchen sink, there had been a couple of vans
and around half a dozen people on the main road nearby. They had been
staring at some water utility 'holes' - the covers of some were open. The
vans were marked with "PRV Maintenance" and a company name (one of the
outsource the work outfits that do most of the work for the utilities -
but I have forgotten which one). Looking up PRV I found only one related
meaning - Pressure Reducing Valve. Could they have done something like
turn up the pressure?

Make any sense to anyone?

Fit in a full-bore mains stop-tap. Then near the kitchen sink tap fit a
small shock arrestor which cost around £10. Sorted.

"Rod" wrote

The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.


Stop cocks are usually used not just as the house shut off valve, but also
for regulating flow around the house.
In replacing this with a full bore ball valve, you have removed this
regulation and are now subjecting your house mains pipework to full
pressure/flow from the external mains. This I think you have realised, as
you are turning down the flow at the external valve now.
Would have been better to replace the leaking stopcock with a new stopcock
to maintain the option to regulate, ball valves full-or-reduced bore are not
designed to control pressure/flow, they are for on-off duty only.

Phil

"TheScullster" wrote in message
. uk...

"Rod" wrote

The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.


Stop cocks are usually used not just as the house shut off valve, but also
for regulating flow around the house.
In replacing this with a full bore ball valve, you have removed this
regulation and are now subjecting your house mains pipework to full
pressure/flow from the external mains. This I think you have realised, as
you are turning down the flow at the external valve now.
Would have been better to replace the leaking stopcock with a new stopcock
to maintain the option to regulate, ball valves full-or-reduced bore are
not designed to control pressure/flow, they are for on-off duty only.

Phil

Surely a stop tap cannot reduce pressure (static) - only "flow".

TheScullster wrote:
"Rod" wrote

The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.


Stop cocks are usually used not just as the house shut off valve, but also
for regulating flow around the house.
In replacing this with a full bore ball valve, you have removed this
regulation and are now subjecting your house mains pipework to full
pressure/flow from the external mains. This I think you have realised, as
you are turning down the flow at the external valve now.
Would have been better to replace the leaking stopcock with a new stopcock
to maintain the option to regulate, ball valves full-or-reduced bore are not
designed to control pressure/flow, they are for on-off duty only.

Phil


Not so in this case. The stopcock under the sink controlled flow to the
tap at the sink and the washing machine only. This is a branch from the
main water pipe (from after the whole house stopcock). (The main run of
which carries on up to the loft, the the cold water and header tanks.)
It would have been more usual, nowadays, to have a service valve of some
sort under the sink.

There was and still is a 'proper' (i.e. normally positioned) mains
stopcock for the whole house supply in the boiler cupboard, where the
actual water main pipe enters the building.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

On Thu, 8 Jan 2009 11:46:56 -0000, Bob Mannix wrote:

As to your banging, this is generally caused by loose pipework whacking
something as it flexes under pressure step changes such as shutting off
a fast flow. One approach would be to get someone else to help and to
try and isolate where exactly the physical bang is coming from and the
direct cause.

The banging needs to sorted out properly. Just fixing the moving bit of
pipe might deal with the audible bang but the hydralic shock will still be
there. Over time that has been known to force apart compression joints...

Cures vary from fiddling with valve to reduce flow rates, pressure
reducers or shock absorbers.

--
Cheers
Dave.

Doctor Drivel wrote:


Fit in a full-bore mains stop-tap. Then near the kitchen sink tap fit a
small shock arrestor which cost around £10. Sorted.

Will that cure the cisterns?

(Cheapest I could find was nearly £13.)

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

Bob Mannix wrote:

They may have been reducing the pressure as they have realised that this is
the cheapest way to meet government leak reduction targets (less pressure,
less water lost). They have a statutory minimum to maintain so pressure and
leak management programmes concentrate on tuning the supply systems down to
the statutory minimum. It is, of course, possible that subsequent to such a
tuning operation (or coincidentally), someone has complained that they are
not getting their statutory minimum or, just as likely, a new development
tacked on the end of the supply pipe is under pressure and the pressure has
been increased to compensate further back, leading to an overpressure in
your road.

As to your banging, this is generally caused by loose pipework whacking
something as it flexes under pressure step changes such as shutting off a
fast flow. One approach would be to get someone else to help and to try and
isolate where exactly the physical bang is coming from and the direct cause.
Whatever the incoming pressure (within normal limits) a domestic
installation should be possible without the banging!


Thanks.

I am certain the pressure has not reduced - at full lick we have a
veritable Niagara coming out the tap! Seems even faster than before.
Can't think of any likely building changes in the area.

Well - I took your pipe looseness comment seriously and, despite being
fairly sure all was well, checked thoroughly. And found one definitely
wobbly pipe and a questionable section. Fixing those solidly has
improved things a bit - but still getting some so I will have to search
for any other possibilities. (The difficulty is that some of the
pipework is seriously inaccessible.)

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

"Rod" wrote

Not so in this case. The stopcock under the sink controlled flow to the
tap at the sink and the washing machine only. This is a branch from the
main water pipe (from after the whole house stopcock). (The main run of
which carries on up to the loft, the the cold water and header tanks.) It
would have been more usual, nowadays, to have a service valve of some sort
under the sink.

There was and still is a 'proper' (i.e. normally positioned) mains
stopcock for the whole house supply in the boiler cupboard, where the
actual water main pipe enters the building.

In that case it would appear that the branch line was acting as a shock
arrestor, rather like a damper, with the reduced bore of the stopcock
providing the damping effect.
As others have said, it looks like it is time to install a proprietory shock
arrestor somewhere to see if this resolves the issues.

Phil

"Rod" wrote in message
...
Doctor Drivel wrote:


Fit in a full-bore mains stop-tap. Then near the kitchen sink tap fit a
small shock arrestor which cost around £10. Sorted.

Will that cure the cisterns?

(Cheapest I could find was nearly £13.)

£3 is going to kill you? The jumper on the stoptap look like it is locking.
A full-bore tap will take shocks back into the mains, the jumper may be acts
as a check valve. But to be sure a shock arrestor near the most used and
offending tap - the kitchen. It should sort it. A 15mm x 1/2" fbsp x 15mm
tee in the pipe under the sink, near the kitchen tap

A full-bore tap may mean you can suffer pressure reductions as it improves
"flow". If they reduce the mains pressure you flow suffers. Remove
restrictions (a stoptap) and you flow improves at a reduced pressure.

"Rod" wrote in message
...

There was and still is a 'proper' (i.e. normally positioned) mains
stopcock for the whole house supply in the boiler cupboard, where the
actual water main pipe enters the building.

Replace this with a full-bore valve.

Doctor Drivel coughed up some electrons that declared:


"Rod" wrote in message
...
Doctor Drivel wrote:


Fit in a full-bore mains stop-tap. Then near the kitchen sink tap fit a
small shock arrestor which cost around £10. Sorted.

Will that cure the cisterns?

(Cheapest I could find was nearly £13.)

£3 is going to kill you? The jumper on the stoptap look like it is
locking. A full-bore tap will take shocks back into the mains, the jumper
may be acts
as a check valve. But to be sure a shock arrestor near the most used and
offending tap - the kitchen. It should sort it. A 15mm x 1/2" fbsp x
15mm tee in the pipe under the sink, near the kitchen tap

A full-bore tap may mean you can suffer pressure reductions as it improves
"flow". If they reduce the mains pressure you flow suffers. Remove
restrictions (a stoptap) and you flow improves at a reduced pressure.

Just an NB: I don't think the "upside down copper bulb" cheap shock
arrestors are suitable for potable water. There are fancy ones with
diaphragms which are, but these cost more.

Certainly worth checking.

Cheers

Tim

"TheScullster" wrote in message
. uk...

"Rod" wrote

The other day I replaced an old and leaking stopcock under the kitchen
sink - with a proper full bore valve.

Stop cocks are usually used not just as the house shut off valve, but also
for regulating flow around the house.

They are not designed for that.

"John" wrote in message
...

Surely a stop tap cannot reduce pressure (static) - only "flow".

yep.

Tim S wrote:
Doctor Drivel coughed up some electrons that declared:

"Rod" wrote in message
...
Doctor Drivel wrote:

Fit in a full-bore mains stop-tap. Then near the kitchen sink tap fit a
small shock arrestor which cost around £10. Sorted.

Will that cure the cisterns?

(Cheapest I could find was nearly £13.)
£3 is going to kill you? The jumper on the stoptap look like it is
locking. A full-bore tap will take shocks back into the mains, the jumper
may be acts
as a check valve. But to be sure a shock arrestor near the most used and
offending tap - the kitchen. It should sort it. A 15mm x 1/2" fbsp x
15mm tee in the pipe under the sink, near the kitchen tap

A full-bore tap may mean you can suffer pressure reductions as it improves
"flow". If they reduce the mains pressure you flow suffers. Remove
restrictions (a stoptap) and you flow improves at a reduced pressure.

Just an NB: I don't think the "upside down copper bulb" cheap shock
arrestors are suitable for potable water. There are fancy ones with
diaphragms which are, but these cost more.

Certainly worth checking.

Cheers

Tim

Drivel,

I put the price in parentheses as a matter of information but not
desperately important. Some were very considerably more expensive.

I asked the question because we are now getting bangs from the sink, the
washing machine, the WC cistern and the cold water tank. So I was
questioning whether putting the arrestor by the sink would be effective
for the others. The thought crossed my mind that the best location might
actually be near the incoming main stopcock.

If I were to fit a full-bore valve (instead of the main stopcock), would
I need to add a check valve? (AIUI, some form of check valve is
mandatory. Or, as they say in Edinburgh, a meringue.)

[And will someone somewhere please decide whether it is 'arrestor' or
'arrester'. Is this another one the trade tends to spell one way and the
rest of the world the other?]

Tim,

The ones I have seen specify 'potable' - anything that didn't, I have
ignored. But worth pointing out.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

"Rod" wrote in message
...

If I were to fit a full-bore valve (instead of the main stopcock), would I
need to add a check valve? (AIUI, some form of check valve is mandatory.
Or, as they say in Edinburgh, a meringue.)

Not mandatory. The shock goes into the mains when full bore. On high
pressure this can still cause thunks when taps are turned off, so a larger
whole house shock arrestor after the maintap is needed.

Change to a full-bore maintap and see. If OK leave. If reoccurs fit a small
arrestor on the most offending tap. If all of them then one large arrestor
at the main tap, or kitchen tap, which is usually first on the line anyway,
and easily hidden under the sink and easy to get at.

Yes use both spelling if searching.