Help! Bristan shower cartridge , cant turn off cold water from shower

[Bettyboo]

Can anyone help please ?
I am in the middle of trying to clean/ service a Bristan shower cartridge for this shower

Recessed concealed shower
1901 Concealed Concentric Shower Valve | Bristan - https://www.bristan.com/products/mixer-showers?code=n2%20cshcvo%20c

It had started to drip after Thames Water installed a water meter outside . I was advised to clean the cartridge .
This morning I started to try and dismantle it to access the cartridge ,and as I started to do this the cold water started to run through the shower more and so I turned the water off . I got so far and could not remove the cartridge as the instructions are not clear and I cant find it on youtube. I am down to the level in the photos, I cant twist or pull the cartridge out . Am I supposed to remove the small plate surrounding the cartridge by removing the circular discs and parts either side of the cartridge ? Not sure how to do this .....I thought the cartridge would pull straight out when I got to this level

I reassembled it without moving the cartridge but when i turn the water on I cannot stop the cold water at all through the shower heads , when i turn the valve it just wont turn off

Please help , its now driving me mad ! thanks

Betty

 

[ShaunCorbs]

there was nothing wrong with it before!, it only started dripping after Thames Water dug up the road and installed meters ! I was left with two dripping showers ! now this carry on... because Bristan sent wrong instructions and sent me off on wild goose chase " oh you can just clean it taking out cartridge and by soaking in water and vinegar ..." Need a large drink and lie down!

Yep common for them to get grit / other things in your water main when working on it which f ups ball valves and showers

 

[ShaunCorbs]

it looks like plastic to me on outside

If you look the part numbers of the thermostatic cartridge are the same so bristan just cheaped out and used plastic towards the end of life of the shower as most parts are discontinued

 

[Bettyboo]

as this is very similar do you think I could try a box spanner as in vid ?
i think builder who installed shower must have kept tool to remove the pistons as I don’t have this either

 

[ShaunCorbs]

There not supplied with the shower listed as an extra

Bristan removal tool - brass | Bristan 100067 | National Shower Spares

Buy a brand new Bristan removal tool - brass (Bristan 100067). 30 day money-back guarantee and same day despatch.

www.showerspares.com