I've noticed that on some close-coupled toilets the syphon valve washer has one side smooth and the other ribbed or, rather, has two concentric grooves. Which way up are these supposed to go? I've always assumed ribbed side down onto the ceramic as if it was up then the outer rib\edge might not make contact with the rim of the syphon.
Just one of things I've never questioned or not seen in instructions.
Just one of things I've never questioned or not seen in instructions.