I was surprised too, but my mum knew about it before that's why we've never done it. When it appeared in the paper advising people to do it Mum rang Thames Water to make sure she was right and they then got onto the council about it. The thing is they don't advertise the fact because then the methods would probably come into question and the water quality would as well "If you can't get rid of that what else can't you get rid of?" sort of thing. I think when levels are low it's not so bad but if everyone started doing it the levels would build and our waterways would get polluted with the stuff.