I take long hot showers after bike rides, so I’m used to the feeling of the water going cold in a shower. What’s interesting to me is that this happens fairly quickly, seemingly toward the end of the supply of water that was hot when you began showering.
But i’ve been thinking about boilers and it’s not clear to me how this works. It occurred to me that maybe the tank only begins refilling with cool water from the pipes once it runs low — but the tanks in most places I have lived are in the basement and don’t have obvious pumps attached. If the tank weren’t full I don’t think you’d be able to maintain constant water pressure upstairs. At the same time, the hot water seems to stay hot for 30+ minutes, even as the tank is presumably refilling itself with cold city water. How does this work? Thanks!
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You got the explanation of how a boiler tank works, but also take the mixer in your shower into consideration.
The water in your boiler will usually be 60°-80°C (140°-176°F) – way to hot for a shower. So you’ll adjust the mixer to get a pleasant 30°C or 86°F. These mixers also have a bit of safety built into them so that you are unable to scold yourself.
The mixer itself has a clever little wax valve that keeps the output fairly the same even when the hot water supply slowly drops in temperature. You wouldn’t notice that the temperature in the tank dropped until the hot water drops below your set temperature.
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