Trevi shower temperature tricky to control

[Amelia1730]

Hello all
We have a Trevi Moonshadow shower which has suddenly become tricky to control. The knob only needs to be turned a tiny bit and it becomes too cool or too hot. It has always been responsive and easy to select the temperature we prefer. When the water is used downstairs it is affecting things in the bathroom. It hasn't made a difference before. Any suggestions or advice please? If anyone has a diagnosis can I solve it myself or do I need to call my plumber? Thank you

 

[Amelia1730]

Bumping. Is it the thermostat that's on the blink or some kind of controller issue? The temp control knob no longer has the control through the temperatures. If the water is too hot and you turn the knob just a few millimetres it is then too cool. Fed up with not enjoying my showers anymore. Thanks in advance.

 

[oldbuffer]

1. I think we are going to need a deal more information before anyone can help:
1.1 What type of boiler (or better still, make and model) do you have?
1.2 What sort of hot water system do you have? Cold water storage cistern in loft, hot water cylinder in airing cupboard OR Combi.
1.3 If hot water cylinder, what type, vented (Over cold tank in loft) or unvented?
1.4 Is hot and or cold water to shower pumped?
1.5 Photograph of shower showing controls.
2. Looking at showerdoc and showerspares suggests that many parts are discontinued. If your shower is obsolete you may well need to replace it.

 

[Amelia1730]

Thank you!
Ideal Logic + system boiler in loft
Cold water tank in loft
Hot water cylinder in airing cupboard across the landing
All water to bathroom pumped
We have very hard water

 

[Amelia1730]

Can anyone help please?

 

[oldbuffer]

1. From the information you've given my first thought would be the shower itself is at fault.
2. Depending how far you feel confident to go, you could isolate hot and cold supplies. The:
2.1. Mixer showers often have filters in each of hot and cold feed, and also non-return valves in each feed. These can get blocked / lime-scaled which can upset the balance of pressure between hot and cold. I'm not familiar with the particular shower you have but I would expect you would have to take the control knobs and face plate off to access these parts if they are present. If you can access them, clean and de-scale.
2.2 Beyond that I would suspect the thermostatic valve cartridge has failed. If you can get one (see post #3) they are usually easy to replace once you have got the old one out.

 

[Amelia1730]

Thank you . We have very hard water so certainly could have scaled up although this seems to have happened suddenly so probably failure of valve cartridge I would imagine. Looks like we might be heading for a new shower if we can't get parts. ☹

 

[Mr Chibs]

FIL had a trevi shower, that was difficult to get warm enough... over the months the pressure had seem to go down the pan too, local plumber said the inner cartridge needed to be replaced... think they said the part was £130+
Parts can be got for older showers, but they are expensive.

It was old... a good 18 years plus.

He's decided to have a new shower instead.