On 24 Feb, 14:41, RubberBiker wrote:
Yes indeeed!
The "there must be 15mm pipework for cold" argument sounds like BS to
me. IIRC the installation instructions made much of the fact that hot
supply must be 22mm right the way through - absolutely true and
reasonable as it greatly increases low pressure flow. But this
statement about the diameter of the cold pipe sounds like some utter
numpty at trevi (mis)reading a leaflet and thinking he's an expert.

As I'm still in ongoing communication with the helpful people at the
Ideal Standard, Trevi section on this problem I'll need to avoid utter
numpty conclusions for now.

I did receive an answer a little while ago to my question about the
minimum 15mm pipe run required and was told:
---------------------------------------
"Unfortunately we do not specify a minimum length for the 15mm run as
we specify the entire run must be 15mm with no exceptions. We cannot
support or guarantee normal operation of the valve outside of these
installation requirements."
----------------------------------------

So if the rising main emerged in the bathroom itself, from there 2
Metres of 15mm pipe would conform to the installation spec.
But as the rising main is 20 Metres away from the shower, the 15mm
pipe run has to be 20Metres long to conform?

The message also added:
------------------------------------------
"If the cold header tank were at the maximum 3.0 metres head, the
stored hot water temperature were up around the maximum 75 degs
celsius, and the cold mains pressure at the minimum 1.5 bar, this will
give the hot water the best chance of getting through if the cold
supply pipework was too large."
------------------------------------------

It'll take me a bit longer to pick the bones out of the second part of
the message.
..
For pressure measurement, screwfix do a cheap gauge that will fit
washing machine taps, and/or outdoor tap fittings:

http://www.screwfix.com/prods/82412/...-Tools/Pressur...

Thanks for the link. Originally I used a tyre pressure gauge from
Halfords but the situation is perhaps getting a little too demanding
for such bodges at this stage,

Dick Treen

On Tue, 24 Feb 2009 07:08:55 -0800 (PST) someone who may be
" wrote this:-

Thanks for the link. Originally I used a tyre pressure gauge from
Halfords but the situation is perhaps getting a little too demanding
for such bodges at this stage,

If the cold pressure is outside the specification then a suitable
pressure regulating valve in the cold would be more useful than a
length of 15mm pipe. However as you have already tried turning down
the main stop tap this may not be the problem.

Have you checked that water does come out of the hot pipe at the
shower and it has not been blocked by some debris? Is there debris
in the hot filter in the shower? Something might have been dislodged
or drawn in while the work was being done.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 24 Feb, 18:13, David Hansen
wrote:
On Tue, 24 Feb 2009 07:08:55 -0800 (PST) someone who may be
" wrote this:-

Thanks for the link. Originally I used a tyre pressure gauge from
Halfords but the situation is perhaps getting a little too demanding
for such bodges at this stage,

...
If the cold pressure is outside the specification then a suitable
pressure regulating valve in the cold would be more useful than a
length of 15mm pipe.

It does seem that way to me, though any tips from experience are
useful and appreciated.
I'm working on the basis that there can't be much stopping the shower
working as there has been so little that's changed since it was.
There are 3 main components in the shower body and I've just replaced
2 of them.
The remaining valve is 145quid+ to replace, so I'm trying to ensure
that all the less expensive changes are made first. I wouldn't want to
spend big bucks only to find it still hasn't done the trick.

However as you have already tried turning down
the main stop tap this may not be the problem.

I'm not certain about that but it does seem unlikely to be a problem
with the cold supply.
Unless I can locate the problem and remove it, I'll be working my way
through the installation spec again and scrupulously ensuring that the
details are followed.
I' don't think I'll be prepared to entirely remove the 22mm cold
supply and replace it with 15mm though. So a pressure regulating valve
may well be next on the list

Have you checked that water does come out of the hot pipe at the
shower and it has not been blocked by some debris?

The flow of hot water doesn't appear to be significantly reduced but
it may be affected enough to cause the shower to fail.
I'm wondering if a mains pressure hose connected to one hot tap at a
time might blow any obstructions back into the header tank where they
could be strained out.
I'm guessing that any debris wouldn't make it back further than the
DHW cylinder though, from where it could eventually be carried back to
the problem area.


Is there debris
in the hot filter in the shower? Something might have been dislodged
or drawn in while the work was being done.

I've spent quite some time cleaning the filters but the way it's going
I'll soon be spending some more.

Dick Treen