I live in Ireland, so those regs don't apply to my situation. But it seems increasingly likely to me that this sediment is being carried through my supply pipe from the watermain on the road. The supply on my street is pressurised from both sides, and we are on the low end of a sloping street, which I am told could lead to a buildup of gunk over time from the corroding cast iron mains in the area. The pressure seems to be low enough in the area to lead to such a condition.
There was a definite improvement in water clarity and colour when I asked the local council to flush the mains two years ago, but it didn't last. I suspect we would not have this issue if the mains were internally relined with plastic interiors, or if it flowed in only one direction. Anyway, I could be wrong, and the problem could be mostly on my side, but it would have to be a really obscure issue at this point. I will have to have an experienced plumber have a look.