Shower valve.

[Monty74]

Hi everyone,
I'm replacing a shower cartridge but need some advice. Can anyone see a way to turn the water off? Their are two large slotted may valves,but how do I turn these? Appreciate any advice! See photos attached.

 

[Rodders53]

Those almost certainly are not isolating valves, but non-return valve / mesh filter covers; as described in that (Reddit?) text box. Follow / trace the pipe route(s) in the wall from those two inlet points and you may find isolators (and equally likely you won't).

If there are no accessible, dedicated isolators for the pipes in the wall to the shower mixer then the main HW tank feed and main stop valve may need to be used and some drain-down via bathroom taps needed.

(I got my plumber to fit full bore isolators in the adjacent vanity unit of our ensuite refurbishment for just such maintenance purposes).

 

[Monty74]

Cheers Rodders.
I turned off the main water last time I greased up the cartridge.