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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The tank stays full because cold water comes in to replace the hot water. Because hot water rises and the hot water is piped out the top of the tank, you go through all the hot water before the cold water reaches the top. There is surprisingly very little mixing of the hot and cold water in the tank.
Alright here is how water heaters work. The hot water pipe is attached to a port in the top of the tank so your hot water is drawn off the top. The cold water pipe inlet has a dip tube. This takes the cold water to the bottom of the tank and prevents mixing as you use hot water. The top of the dip tube has a small hole in it to prevent back siphonage if there is a break in the cold water line.
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I dont know if its like here in Iceland in other countries, hot water comes from the ground at 90c
its around 70c when it comes into your house, used for heating the house, showers even washing machines that are designed to use hot water (they are getting rare these days)
so we have endless hot water, most blocks and houses have the front pavement heated with the run off from the radiators, its still 20c when leaving the house so its a second free use
dont having to shovel snow is very nice
Thank you, now I can shower without fearing that the hot and cold water will come together like oil and water!
The water in the tank is always hot. When you turn on the hot water, you get that hot water. Once that water is used up, you’ve run out of hot water, and you need to wait for the tank to heat up again.
Heating water takes a lot of energy, so it’s a very slow process. Generally, there are two heaters, one on the bottom and one in the middle. When you start using hot water, cold water enters the bottom, and the bottom heater turns on. Now that water doesn’t get hot, but it does gets warm. Once you have used enough hot water that the warm water reaches the second heater, that turns on to get that warm water to become hot water. This gives you a hot water capacity of about 150% the volume of the tank before its too difficult to keep up the demand.
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So a boiler works with a heating coil that is super hot. Water passes through it and gets heated and gets to you. You may run out of hot water though if your water pressure is greater than what the boiler is rated at.
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