The outlet probably turns outward, so it’s not just vertical movement.

Ah, I did not think of that. So I need to scrap the idea of a rigid pipe going into a rubber bushing. I guess an accordian pipe would be the viable cheap hack, apart from some way to add support just around the drain.

Maybe there was some kind of metal support that got left out during installation?

The toilet fell through the floor at one point because (I’m told) the house flippers neglected to use backer board wherever they layed tiles (kitchen and bathroom).

no, I have never maintained a pool so I don’t know anything about that. Though someone mentioned there is some kind of material in a brick form that goes in the cistern. Not sure if that does the same thing.

Brick acid may be hydrochloric acid.

Ah, that reminds me… I do tell guests when a party is getting a bit edgy to obviously do their vomiting in the toilet, but to not flush since vomit is rich in hydrochloric acid… to just leave it there to work on the scaling. I guess it doesn’t happen enough.

Water softeners are a bit of a double edged sword. They solve the limescale problem but then soft water is more conducive to corrosion in appliances like hot water tanks. I guess I would not run a soft water circuit just for toilets. OTOH, a friend has a rain water harvesting tank which feeds the cisterns. I suppose that’s not just a water savings but probably solves the limescale issue.