Triton T80si

[Toffee]

Half an hour ago I fancied a nice hot shower. The experience was not enjoyable. The water temperature alternated from scalding to freezing about every 15 seconds, and no matter where I set the controls it was the same. What is wrong and do I need to replace a part or the whole unit?

[qapmoc]

Many of these units have a pressure regulating valve built inside the control valve, sounds like you are having trouble with this and the water flow is too low and the water is getting too hot then the overtemperature control switches off the heat and it cools down and switches on the heat and so on in a hot->cold->hot->cold loop.

[rccatnap]

I have a MIRA power-shower with a temperature control. Every nine months or so, the temperature becomes erratic and this is due to calcium build up that makes the mixing sleeves stick. Using the instructions that came with the unit, I turn off the water and dismantle the control. I soak the internal parts in descaling fluid for half an hour, smear the sleeves with a little silicone grease and reassemble. After about twelve years of doing this, the plating inside became so thin, I had to replace the internal mixer unit, which came as an assembled unit. That was a year ago and no sign of any problems yet.