Lots of hot comes out the sink taps, but the shower is stone cold. The HW pipe feeding the shower goes from lukewarm to cold-water-incomer-cold as the shower runs. It worked fine before, and they're adamant no plumbing has been done.

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't see what else could be happening. Plan to take a look tomorrow.


NT

On 19/12/16 01:15, wrote:
Lots of hot comes out the sink taps, but the shower is stone cold. The HW pipe feeding the shower goes from lukewarm to cold-water-incomer-cold as the shower runs. It worked fine before, and they're adamant no plumbing has been done.

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't see what else could be happening. Plan to take a look tomorrow.


yes. had that happen here.

Until I fixed the issue.


NT

On Sunday, 18 December 2016 23:15:33 UTC, wrote:
Lots of hot comes out the sink taps, but the shower is stone cold. The HW pipe feeding the shower goes from lukewarm to cold-water-incomer-cold as the shower runs. It worked fine before, and they're adamant no plumbing has been done.

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't see what else could be happening. Plan to take a look tomorrow.


NT

You'll probably find there are check valves (non-return) in the shower mixer.
One has likely jammed open.
Cold water is transferring to the HW system
Just needs cleaning/freeing off inside mixing valve.

Happens in limescale areas.

On Tuesday, 20 December 2016 15:23:58 UTC, The Natural Philosopher wrote:
On 19/12/16 01:15, tabbypurr wrote:

Lots of hot comes out the sink taps, but the shower is stone cold. The HW pipe feeding the shower goes from lukewarm to cold-water-incomer-cold as the shower runs. It worked fine before, and they're adamant no plumbing has been done.

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't see what else could be happening. Plan to take a look tomorrow.


yes. had that happen here.

Until I fixed the issue.

I pretty much worked out what was going on while writing that post. It needed a new hose & head, the hose metal was disintegrating, and the head was largely clogged.

I should make one correction... no mayonnaise was involved. AFAIK.


NT

formulated on Sunday :
The system: Immersion heated HW cylinder, gravity feed. Old thermostatic
mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't
see what else could be happening. Plan to take a look tomorrow.

NRV's or the design of the outlets should prevent back feeding from
either H to C or C to H, so as to avoid contamination of the CW mains
supply.

On Wednesday, 21 December 2016 10:32:12 UTC, Harry Bloomfield wrote:
tabbypurr formulated on Sunday :

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic
mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't
see what else could be happening. Plan to take a look tomorrow.

NRV's or the design of the outlets should prevent back feeding from
either H to C or C to H, so as to avoid contamination of the CW mains
supply.

then I guess there aren't 2 NRVs. Preventing hot going into cold is the one that matters.


NT

On Wednesday, 21 December 2016 11:16:43 UTC, wrote:
On Wednesday, 21 December 2016 10:32:12 UTC, Harry Bloomfield wrote:
tabbypurr formulated on Sunday :

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic
mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't
see what else could be happening. Plan to take a look tomorrow.

NRV's or the design of the outlets should prevent back feeding from
either H to C or C to H, so as to avoid contamination of the CW mains
supply.

then I guess there aren't 2 NRVs. Preventing hot going into cold is the one that matters.


NT

Cold going into hot water can cause floods. So that matters too.

The Natural Philosopher Wrote in message:
On 19/12/16 01:15, wrote:
Lots of hot comes out the sink taps, but the shower is stone cold. The HW pipe feeding the shower goes from lukewarm to cold-water-incomer-cold as the shower runs. It worked fine before, and they're adamant no plumbing has been done.

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I don't see what else could be happening. Plan to take a look tomorrow.


yes. had that happen here.

Until I fixed the issue.


:-)

--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

harry laid this down on his screen :
On Wednesday, 21 December 2016 11:16:43 UTC, wrote:
On Wednesday, 21 December 2016 10:32:12 UTC, Harry Bloomfield wrote:
tabbypurr formulated on Sunday :

The system: Immersion heated HW cylinder, gravity feed. Old thermostatic
mixer shower past its best. Mayonnaise pressure cold.

I suspect the shower's cold feed is backfeeding the HW supply pipe. I
don't see what else could be happening. Plan to take a look tomorrow.

NRV's or the design of the outlets should prevent back feeding from
either H to C or C to H, so as to avoid contamination of the CW mains
supply.

then I guess there aren't 2 NRVs. Preventing hot going into cold is the one
that matters.


NT

Cold going into hot water can cause floods. So that matters too.

Our mixer taps have internal concentric pipes, so the mix only occurs
at the end of the spout, so as to prevent any reverse flow.