Shower scalding

[Johnking]

I'm trying to fix a shower that has developed binary temperature control! A slight turn of the knob changes it between two states, cold and scalding.

It's a Crosswater thermostatic valve connected to a Vaillant combo, mains pressure. Everything is over a decade old. The water is very hard, lots of limescale.

I suspect the temperate control cartridge, but before I buy a replacement, is there anything I can do to confirm this is the problem? And is the old one repairable?

Thanks,

John

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[Madrab]

I'd advise you get in touch with showerdoc.com, they'll be able to advise what your best options are.

 

[Johnking]

I'd advise you get in touch with showerdoc.com, they'll be able to advise what your best options are.

I'm sure that's good advice, but I was hoping to be able to discuss it a bit with people on here!

 

[Madrab]

No bother John, it's up to you of course.
Showerdoc are the consummate professionals when it comes to shower problem diagnosis and spares availability, that's all, giving you the quickest way to get your shower fixed.
It certainly sounds like a thermostat issue as you suggest, given that's what controls the hot n cold mix. If it's a Crosswater Ultra, there is a service kit you can get.
If it's a single thermostatic cartridge type then I believe they need to be replaced complete.
The neat lemon juice trick to break down the limescale may help.

 

[Johnking]

The neat lemon juice trick to break down the limescale may help.

I did strip it down a bit and soak it in diluted spirit of salts. No dice.

What I really wanted to find out is whether other problems in the system might be the cause, for example I've seen posts about missing non-return valves and boilers cycling. That said, the temp control is incredibly stiff to turn and shifts from hot to cold with the most microscopic of turns, so it does seem most likely.

 

[hazetimesfive]

If it's stiff it's likely kaput . Replace crosswater cartridges all the time here