Well you will know there is only TSE and potable water then. Also I never memtioned about legality of private car wash or otherwise, only what the public water supply is fit for.

I am in the water industry and know the operational and maintenance problems from the works to the distribution system. I wouldn't drink the water. You may think you are alright but the effects may be longterm.

You may want to take a look inside the tank on your roof if you don't think twice about drinking then your standards are pretty low.