zlacker

> like separate cold and hot water faucet

This was, oddly, for regulatory reasons; the concern was that a blocked mixer unit could cause hot water (considered potentially unsafe) to be forced into the mains supply (presumed safe). This hasn't been a concern with mixer designs for a long time, but it took til the 90s to get the rule changed.

>>rsynno+(OP)
The hot water was considered unsafe initially because early hot water cylinders over there were open tanks subject to incursion by vermin

>>FredPr+l5
This is a weirdly persistent myth, but no, that's not the case (think about it; what would happen if you had an open hot water tank? It would cool down very quickly, and you'd have horrendous humidity problems). _Cold_ water tanks used to be like that (sometimes still are), which I suspect is where the confusion comes from.

Hot water getting into the mains would be a concern anywhere; in particular, unless all equipment is in perfect working order, there's a legionnaires disease risk, but there are many other risks.

>>rsynno+(OP)
Thanks for the details! (Completely randomly just a few hours ago I got a many-many years old Tom Scott video recommended to me on YT about this topic.)