How to access the filters on this bath/shower mixer

[alextwospoons]

I need to take out the filters to descale them, however they are behind the brass discs with the slots, but i cant unscrew them for love nor money, is there a special

tool or magic trick

 

[Aquarius]

Flat bladed screwdriver? A 10mm tip one?

 

[alextwospoons]

Flat bladed screwdriver? A 10mm tip one?

I have tried an 8mm one and a 12mm chisel, I will buy a fat L shaped one for leverage tomorrow, thanks anyway

 

[ShaunCorbs]

Wera do some with spanner flats on them

https://www.amazon.co.uk/Wera-932-Screwdrivers-Chiseldriver-Multi-Colour/dp/B003ES5KSM/ref=mp_s_a_1_1?dchild=1&keywords=wera%2Bdemolition%2Bscrewdriver&qid=1598222016&sprefix=wera%2Bdem&sr=8-1&th=1&psc=1