Dismantling thermostatic mixer cartridge

Apr 26, 2018 5 Replies

The temperature control of our bar mixer tap/shower became very stiff (almo st unturnable) so I removed it today and free it up with a pipe wrench. Whi lst it's a lot better I really want to find out exactly what caused it to s eize and perhaps prevent it happening again.



The problem is, I can't seem to dismantle the cartridge any further. The ca rtridge is as shown here:



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The circlip was removed from the position it is sitting below, and this has allowed the centra shaft to be pushed in for ~5mm. With a normal tap cartr idge it would of course be possible to push it all the through but in this case I think it is what I assume to be the thermostatic element at the othe r end preventing this:



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With pliers I can rotate the red plastic ring ~180 degrees but it doesn't a ppear to be unscrewing. Before I break anything (the cartridge is working n ow, at least for the time being) does anyone know how to remove this ring/e nd, assuming that's what I need to do?


Soak it in de-scaler for a bit, see if that frees it up more?

Be careful about soaking anything in de-scaler if it contains plastic bits. De-scaler can melt some plastics with time.

Might white vinegar be better? Not quite as fast on the scale, but gentler on the plastics perhaps?

I'd love to know. The old Rover has a screen washer jet which produces a fine fan like spray. Works beautifully when clean, but the factory obviously hadn't heard of hard water. It just unclips easily so I have a spare which I clean with de-scaler. But left it in that for a couple of days and it melted. The body is PVC or similar.

Some cartridges have left hand threads (my mira 915 does) so you have to know which way to screw it.

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