I've just been speaking to one of my lecturers about a thesis on improving software that maps pesticide spread in watersheds; software that the Uni originally designed for the water company Severn Trent. (:) doing work for once!)
Anyway, we got talking about Severn Trent and apparently they ADD PHOSPHATES to the water supply deliberately!

The reason is that large doses of phosphates help to "coat" lead pipes, but that the coating wears off within a month so constant treatment is required.
Not much help for fish keepers, but I suppose it helps keep people alive

. Might explain part of the large increase in phosphates we've had in the UK in the past decade or so. He didn't know for sure, but strongly suspected that all UK water companies do this. They aren't my local water company but it'd be worth finding out from one's local supplier whether they do. Water companies might not do this elsewhere in the world; who knows?
Don't know if you all knew this and this terribly old news or not.