On Fri, 05 Jan 2018 17:35:56 -0000, "James Wilkinson Sword"
wrote:


Just had a check, in England, tapwater is kept under 1ppm. Pool water is kept under 5ppm. So 5 times as much, not the same.

I just looked again and that web site I linked had the decimal wrong
it is 1-3 PPM