We cant have it for free.It costs a lot of money to get it to the taps.It has to be paid for.If we have to have it supplied to our houses we should each pay according to usage, just like we do for gas and electric. It cant be fair that the 80 year old widow who hardly uses any, pays the same as the family of 4,5,6 etc living next door. 
Sounds a little like the argument for the Thatcher (Poll) tax Albs.
Example . Two adults and their four adult children (all on minimum wage) living in a council house end up paying six times more than a single man living in a two hundred room castle.The wealthy just loved the Poll Tax
That was never the plan, just the headlines in the papers.

I would much rather have the poll tax reintroduced than the ludicrously expensive shambles we now have - the council tax.
It has been a licence for councils to print money, and they have printed it like its going out of fashion.

Getting back to water - I dont see how anyone can try to justify paying a flat amount to use how ever much they feel like using. Simple logic dictates that it will be subsidised by someone else.

Ive always been a believer in paying my own way in the world.
It may also come as a surprise that I tend to agree that water should never have been privatised.