I was thinking about scaling. Is it a particular hard water area?
Brian

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On Thursday, 10 October 2019 11:15:50 UTC+1, Tim+ wrote:
tabbypurr wrote:
On Thursday, 10 October 2019 10:08:08 UTC+1, Tim+ wrote:

A while back a friend asked me if there was any way he could have a
warm
water supply outside for washing his dog.

As there was easy access to hot and cold supplies inside I fitted one
of
these.
https://www.bes.co.uk/thermostatic-m...-3-15mm-12162?

Before purchase I checked with the manufacturer that it was suitable
for a
mixed mains pressure cold feed and gravity fed HW.

It worked fine for several months but then water stopped coming out of
the
tap. Sometimes if you waited the flow would start and it would produce
premixed warm water. Eventually it stopped working altogether.

Thinking that he'd just been unlucky my friend opted to buy a new valve
and
now a month after fitting the same thing is happening. All rather
annoying.

Before fitting the new valve I blew through the non-return valves and
discovered that they needed a fair bit of pressure to persuade the
valve to
"crack open" the first time, after that they seemed to open reasonably
easily.

It seems likely to me that the HW non-return valve is sticking on its
seat,
perhaps because it's being exposed to reverse mains pressure cold water
when the outside tap is off.

Now I'm sure I could disassemble the things and blow through the valve
again to free it but I would really rather not have to keep doing this.
One thought that occurs to me is that if I could think of a simple way
to
produce an upstream "pressure pulse" above the non-return valve I could
pop
it off it's sticky seat.

Long term answer may be to just go back to external H & C taps but he
does
like the pre-mixed warm water.

Any suggestions?

Tim

So fit a mixer tap without the tmv.

Prefer not to have a mixer tap outside exposed to the risk of frost. I

is it somehow worse than a single tap exposed to risk of frost?

imagine any internal blender valve (thermostatic or not) will have
non-return valves.

Tim

and any internal blender valve will scale & fail. Make your choice


NT