Mira shower problem

[MadAlicesDad]

We have a Mira Coda shower fed from a Salamander shower pump. The HW comes from a Surrey flange on the HW tank and the CW comes directly from the CW tank in the loft. All pipes before the pump are 22mm, after it is a mix of 15mm copper and plastic. It was all installed about 4 years ago.
The shower has recently reduced in flow and started pulsing, often accompanied by the pump sounding like it is cavitating. If I disconnect the pump, the shower seems to run ok, but with reduced flow.

I've removed the shower unit and the mesh filters on the inlets are clean, but we do have hard water and scale is a problem. I suspect the thermostatic cartridge in the shower could be clogged. Does this sound plausible or could it be the pump?

If it is the cartridge, how do you get it out? I've removed the large 'nut' and the cartridge will turn, but I can't get it out of the shower unit. Any tips greatly appreciated.

Cheers
Mike

 

[Charnwood]

Pages 17 & 18 may help.
http://www.mirashowers.co.uk/onlinecatalog/pdf/1065367_w2_h_mira_coda_bar_valve.pdf

 

[MadAlicesDad]

Pages 17 & 18 may help.

Unfortunately not (but thanks for the suggestion).
I've got the diagram so know how it goes together, what I can't find is any instruction on how to dismantle it. From looking at pictures of the replacement cartridge, there are three O rings holding the cartridge in place (along with a build up of scale).
It doesn't seem to screw in (I can rotate it with the 'temperature stop assembly') but there is nothing to grip to pull it out (other than mole grips that might damage it)
How do you pull it out?
TIA
Mike

 

[Charnwood]

View media item 65389

 

[MadAlicesDad]

It's actually the later (post 2008) design shown in the link you posted earlier which has a longer threaded retainer, but the principle is the same. Unfortunately the longer retainer means the bit that contacts the unit is even deeper in the hole . I have removed the retainer but the cartridge still only rotates.

I spoke to Mira technical support earlier. They offered no real advice; it should just pull out! Probably does when new, but with not with limescale.
I'll try again tonight but I am keen not to damage anything so will keep BFH use to a minimum.
Mike

 

[Charnwood]

Bus Fare Home? Ey, this is what you could've won (a bl00dy caravan). You can't beat a bit of bully.

I was talking Brute Force and Ignorance.

 

[MadAlicesDad]

I meant Big F*****g Hammer. Same principle, different tool!
Cheers,
Mike

 

[MadAlicesDad]

Knowing that it should just pull out, I didn't need ignorance, just brute force! It came out with pliers and a bit of levering.
There's no obvious scaling, who knows what's inside? I've put it all back together but still have reduced flow. I'll check the pump and a few other things (new shower head) before I buy a new cartridge.

Mike

 

[Charnwood]

Just a thought, there are no filters fitted inline on the pipework, are there?

 

[MadAlicesDad]

Good point, there are probably some on the pump inlet. If so, that could explain why the filters on the shower were so clean.
Will look tonight.
Cheers,
Mike