Do they really check that?
If it comes out your tap its your water isnt it??
My half year bill just came in, it was £234.
So, far as im concerned, im paying for it, il do what I want with it, and they can do one if they dont like it.
Thats like a bank telling you how to spend your money.
As far as pouring it down a drain, its harmless chems, as said, no worse than car shampoo.
Forget about it!!
Rich