Trevi thermostatic shower valve - no hot water any more

2 Nov 2013
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United Kingdom
This thermostatic shower valve (Trevi CTV Built-in A3102AA) has gradually got worse since I moved into the house 3 years ago. It used to work most of the time eventually kicking out hot water but gradually got worse. It would probably have been professionally fitted as the rest of the house appears to be fitted professionally so I wouldn't expect any DIY to be involved.

I had a workaround which was to lower the shower head to the bath (empty) and run it - cold water would trickle out until eventually the hot water would kick in.

This got gradually worse and now I get no hot water no matter how long I run it with the head lowered.

Would a new cartridge (£133) be the answer?

The fault guide (CTV Diagnostic Chart) supplied mentions "Outlet temp too cold" and suggests "Airlock/partial supply blockage".

It is a gravity fed mains system with an immersion heater. It is piped from the attic. My hot water and my cold water comes out at a good pressure.

I have been ignoring the problem for ages now so best get it sorted. A mate suggested connecting it to my pump used for the ensuite shower but surely as this used to work something must be up.

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I do think plumbing can be a bit of a dark art going by the zero number of responses/suggestions. As an engineer I can understand that fitting a complete system is technically ideal but fixing something that someone else installed can be problematic.

For anyone that follows this thread I bought a new cartridge (£130). My plumber thinks that the system was installed wrongly.

The plumber wants to run a cold water pipe from the tank in the attic rather than have cold mains over powering the valve. If that works we can also change the cartridge as it might not be in the best state after such intermittent history and being hammered by the high pressure cold main. I just need to remove a few tiles for him to do that - he didn't seem to want to get involved in that side of the job.
It will never work properly unless supplies are same pressure !!
Cartridge could still be fooked though .

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