We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Dave Liquorice"
saying something like:

Depends where you are and how hard your water is. When we lived in St
Albans it was hard and full of odd metal minerals as well, the kettle
would need descaling every few weeks and the scale was some lovely
colours of green and blue, borehole water I think.

When I moved in here I had a borehole, the water from which did exactly
as you describe. I've been connected to the public mains for years and
now have a borehole for sale, if anyone's interested.