This is leaking from the top valve and needs replacing – but how on earth do you get the moving top mechanism off? I’d rather not change the feed pipe if I can. The notched pipe from the bottom from cistern is fixed – the rest moves up and that but off the top as far as I can work out.

Turning off the water is a nightmare.

I would guess it is not designed to come apart. Probably a throw away part and is one part to the external fitting. Worth having a prod though. You’ll need the water of either way. I’d turn the water off then for an isolator valve to make future jobs easier.

Usually a full replacement.

😳 Posted from my phone in the pub earlier. Should say: You’ll need the water off either way. I’d turn the water off then fit an isolator valve to make future jobs easier.

Just replace it with a fluidmaster, isolate water add valve for future maintenance. Flush cistern drain rest into waterproof bag or soak up remaining water. looks like a lab sanitary button syphon and bottom entry float.

If you purchase the fluidmaster set you have a spare syphon too as it will fit onto existing hardware without removing cistern to replace .

Do you know what it is? When I eventually found out exactly what system mine was a very helpful video on YouTube showed me the really quite obvious quick release clips to get it apart.