Triton Capella Thermostatic Mixer Shower

You need to check the filters and gate valves coming to the shower to make sure that they are clear and open. If they are then it maybe that the thermostatic part of your thermostatic cartridge is faulty, and then you will need to replace the part below,

http://www.showerdoc.com/TRITO-83308580-Triton-Thermo-Cartridge-Cappella-83308580

First check that the filters on the cartridge are clean and clear

If you are on a combi boiler then carry out the following check

Regarding the temperature fluctuation or cool running it could be a faulty cartridge however to check this, see if you can get hold of the hot supply pipe before it enters the shower or perhaps as it leaves the boiler.

If when holding this pipe the temperature fluctuates or is cool then the problem is not with the shower but more likely with the boiler as the shower can only deliver what the boiler sends to it.        

Mostlikely the non return valves in the inlets

http://www.showerdoc.com/TRITO-83307290-Triton-Non-return-Valve--x--2-----Does-NOT-come-with-extra-Seals-83307290

Sorryno photo however part 8.

http://www.showerdoc.com/trito-parent-248-triton-capella-thermostatic-mixer-shower

Regarding the temperaturefluctuation or cool running it could be a faulty cartridge however to checkthis, see if you can get hold of the hot supply pipe before it enters theshower or perhaps as it leaves the boiler.

If when holding this pipethe temperature fluctuates or goes cool then the problem is not with the showerbut more likely with the boiler as the shower can only deliver what the boilersends to it.        #

Disregard the temperature atthe taps as they have a different flow rate.

Also this valve is designedfor roughly equal water pressures so if you have high pressure cold (mains)Then you may need to fit a pressure reducer/flow restrictor in the cold side ofthe valve