How to change a mixer cartridge

After water is turned off at the mains water supply, remove the hot/cold indicator button from the handle by carefully prising out with a craft knife, flatblade screwdriver or similar.
Loosen the Allen Grub screw within and remove the handle
Undo/remove chrome collar trim and unscrew large hexagonal brass retaining nut then remove the cartridge (making note of the lugs at the base)
Make sure that the seal is not on the valve seat after removing the cartridge
Insert the new cartridge, ensuring the locating lugs at the base are in place
Tighten down the brass retaining nut – correct torque is achieved by about a half turn tightening with a spanner
Fit the collar trim, replace the handle and tighten grub screw, and re-insert the hot/cold indicator.

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