Well done Hillary & Jeremy I rated this show as tops and I did this after I heard you were discussing the water in our dams are low.
Being a retired plumber I have written to councils on both sides of the Tasman about the plastic low down cisterns with underwater valves.
A silent unseen waste of water trickling into the wc pan 24/7 millions of gallons of water wasted annually on both sides of the Tasman.
As a plumber I challenge you to check all your wc pans in your building by placing a square of toilet paper at the rear of the wc pan below the flush pipe. The toilet paper is the same as blotting paper and shows if any water is running into the pan unseen.
I can go into a building with 10 to 12 pans and I can almost guarantee half or more are running into the wc pan. Why dont councils ban them and use syphonic valves is because it is revenue to them 24/7.
I challenge you to try what I have stated above.
Kind Regards Roydon Griffiths