No, the real reason had nothing to do with electricity. In fact dual taps were entrenched before electricity was common place. Mythbusters have done several de

No, the real reason had nothing to do with electricity. In fact dual taps were entrenched before electricity was common place. Mythbusters have done several demonstrations over the years of what happens when you take a hot water heater, disable both of the over pressure valves, and break the thermostat so that it doesn't turn off. They explode spectacularly. Early water heaters had zero overpressure valves. And thermostats are not particularly reliable even today. So exploding a home wasn't particularly uncommon. In the UK, they made a low tech solution to this problem. Look in your toilet, in the back. There is a level sensor. If there is insufficient water, more is added. Imagine taking a large one of these and putting it in your attic. When you drain out of it, gravity provides the pressure. Now put a heater under it attached to a thermostat. If the thermostat fails, either you have cold water (failed closed) or boiling water in your attic and there's fucking steam everywhere (failed open) but you notice and shut it off. If the level sensor fails, you either get water pouring into your house and you turn it off, or the hot water turns off and you investigate. Under no circumstances can pressure build up and explode the house. Of course in like the 1880s better safety mechanisms were developed so it's fucking ludicrous it's still like this but whatever I'm not the king of england. edit: I forgot the punch line. These are open top devices so all manner of shit got into your hot water. They kept separate taps to ensure that when you were pouring cold water for food, you knew it was clean and not contaminated with your hot water. Why they're ok with showering in shit water is something you'd have to ask a Brit.