With a UK-style arrangement, where hot taps give you water that’s been stored in an internal tank in your house rather than coming straight from the water main (… actually, is that particular feature UK-only? Unless you have “on-demand” water heating, which is I think generally not very efficient, your hot water will have to have been stored somewhere, no?), it seems to me that in addition to Legionella you should be concerned about (1) other nasties growing in your water tank and (2) increased leaching of contaminants not only because the water’s hot but also because it’s had more time for the leaching to happen.
I think the main difference between UK and US hot water systems is the pressure. They both involve pre-heating a tank. In the UK it’s common for the hot water tank to be at atmospheric pressure, so the pressure at your hot taps is from the height of the tank above them. In the US, the hot water system is more usually sealed and at mains pressure.
The noteworthy bit of the UK arrangement is the habit of having 2 taps per sink, not the habit of having a hot water heater at all. I am not aware of any cities with municipal hot water supplied in the way that cold water is—the closest thing I know of is steam systems that can supply heat to large areas, but I’ve never seen anyone suggest drinking the water from those. Steam hot water heaters are available to purchase, which suggests they might be used in areas with steam for heat.
Most places I’ve stayed in the continental US have had each building’s hot water provided by a heated reservoir of some sort. The off-grid options I’ve seen are the high-tech on-demand water heaters you mention, or the old-fashioned wood stove water jackets and solar roof heaters.
When I’ve asked friends who drink or cook with hot tap water why they’re ok with doing so, their answers have been along the lines that the risk of harm is relatively tiny in modern homes with everything built to code, compared to the convenience of having the water boil that little bit faster. I’ll keep my cultural superstition of only drinking from the cold tap, but I do see where they’re coming from in reasoning that they know that newer plumbing doesn’t contain any of the “really bad stuff” like lead.
With a UK-style arrangement, where hot taps give you water that’s been stored in an internal tank in your house rather than coming straight from the water main (… actually, is that particular feature UK-only? Unless you have “on-demand” water heating, which is I think generally not very efficient, your hot water will have to have been stored somewhere, no?), it seems to me that in addition to Legionella you should be concerned about (1) other nasties growing in your water tank and (2) increased leaching of contaminants not only because the water’s hot but also because it’s had more time for the leaching to happen.
I think the main difference between UK and US hot water systems is the pressure. They both involve pre-heating a tank. In the UK it’s common for the hot water tank to be at atmospheric pressure, so the pressure at your hot taps is from the height of the tank above them. In the US, the hot water system is more usually sealed and at mains pressure.
The noteworthy bit of the UK arrangement is the habit of having 2 taps per sink, not the habit of having a hot water heater at all. I am not aware of any cities with municipal hot water supplied in the way that cold water is—the closest thing I know of is steam systems that can supply heat to large areas, but I’ve never seen anyone suggest drinking the water from those. Steam hot water heaters are available to purchase, which suggests they might be used in areas with steam for heat.
Most places I’ve stayed in the continental US have had each building’s hot water provided by a heated reservoir of some sort. The off-grid options I’ve seen are the high-tech on-demand water heaters you mention, or the old-fashioned wood stove water jackets and solar roof heaters.
When I’ve asked friends who drink or cook with hot tap water why they’re ok with doing so, their answers have been along the lines that the risk of harm is relatively tiny in modern homes with everything built to code, compared to the convenience of having the water boil that little bit faster. I’ll keep my cultural superstition of only drinking from the cold tap, but I do see where they’re coming from in reasoning that they know that newer plumbing doesn’t contain any of the “really bad stuff” like lead.