"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