Cold water overwhelming hot to showers

[RichardWoking]

Recently 2 of my showers stopped producing hot water following a plumber refitting another of my ensuites. The 2 showers in question are pumped with a Salamander twin house pump. Hot is reaching the showers (hot feed to mixer is hot), yet both showers are luke warm, at best. The other recently refitted shower/ensuite is not on the Salamander pumped system so doesn't suffer the same issue.

The plumber suggested thermostat cartridges in both showers had failed at same time - replaced one cartridge, same problem. He then suggested the hot side of the twin pump had failed, so we restricted the cold intake from the water tank which had some beneficial effect, although the showers were then unpredictable - either scolding hot or freezing cold, both with little or no response from changing the thermostatic settings.

I then purchased a new Salamander twin pump (same model, albeit newer and universal head) and still have the same problem - cold/luke warm showers and the hot reaching the showers but not coming through. It's as though the cold is overwhelming the hot through the thermostats.

Any ideas please?

 

[Chuck]

Your plumber's suggestions are all reasonable initial guesses. (Well the simultaneous failure of two cartridges was a bit of a stretch but...)

It seems to me that something is restricting the flow of hot into the pump or between the pump and the point it splits to provide separate feeds to the two non-working shower.

Possibilities in rough order of likelihood:

A valve (esp. a gate type) that was closed during the refurb and has not been fully opened again.
A temporary plug, e.g. in the feed to the HW cylinder, that has been forgotten about.
A filter that has debris in it.
A piece of pipe (particularly plastic) that has been crushed, or twisted.

I'd probably start by checking the flow rate arriving at the pump, which will tell you which side of the pump to look for issues.

If you want some more specific suggestions, please post few photos of your pipework and some more information about your system.

 

[EvilDrPorkChop]

Did the issue only start after the other shower in the new en-suite was fitted?

 

[John.g]

If the pump is not just a shower pump then you should be getting hot water from a hot water only tap.
You could also turn off the HW cylinder heating and drain/run off until it gets cool/cold, then try the showers on maximum HW setting and see if any flow then.