Hello everyone, recently my city has been doing some repairs to the city’s hot water system and i was without hot water for about 3 weeks.
That got me wondering, how exactly does this work? I read something about a heating agent but i don’t know what that means. And how does the water stay hot while travelling from the place it gets heated to our homes?
Thanks!
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It may not be the same everywhere but there are a few ways you can do this.
You can circulate water in a loop, not a straight pipe, so it comes back to be re-heated if it isn’t used immediately. This is how tall apartment buildings and hotels keep hot water immediately available on top floors.
You could also put some sort of heater in distant locations. This could be electricity though that can be expensive/inefficient. More likely it would be gas, another way you could do it is sending steam out from the same plant that originally heated the water, but this doesn’t necessarily make things any cheaper or easier vs running a loop and re-heating the water as necessary.
The pipes would also be insulated of course. Water actually holds an enormous amount of heat energy so if there is no easy path for a lot of heat to quickly escape, the water is going to stay hot for a while.
Where do you live that hot water is centrally provided? Where I live (USA), we only get cold water supplied to our homes and have in-home water heaters.
I mean, the hot water heater is physically inside your house. Hot water doesn’t have to travel all that far in order to get to your sink or shower.
My understanding is that municipal hot water systems are REALLY rare, according to wikipedia there’s something like 20 cities in the US that do this.
In the vast majority of the country only cold water is supplied by the city. Every home (or building) has a method of heating the water on site and it’s only at that point that it breaks into 2 pipes (1 hot and 1 cold). There’s a few methods for heating the water but the most common is a hot water tank (gas or electric), other homes have an “on demand” hot water heater that’s attached to the home’s furnace.
To answer your question, the pipes are insulated so the water stays hot while traveling.
A large city by me in the Midwest US has hot and chilled water for heating and cooling buildings down town. This is recirculated back to the district energy buildings with many giant boilers for hot water and cooling towers outside for the chilled water.
These are supplied to buildings for HVAC use. Most of the large buildings downtown are on domestic instead of having their own boilers and cooling equipment.
Cold potable (drinking water) is supplied and run through a heat exchanger where the domestic hot loop heats it up to make hot water for showers etc. The now colder domestic hot goes back to the district boilers to be reheated.
Domestic hot water supply wouldn’t be consumed at least here in the states it is used in coils that make hot or cold air and heat exchanges to make potable hot water.
If properly insulated, water can remain hot for a long time. Without the ability to steam away, or transfer the heat elsewhere, water is very good at storing a lot of energy. And if you have one larger and more efficient heating system, as opposed to many smaller and less efficient systems in every home/building, it can be viable on cost and efficiency.
Thank you everyone for the answers, i googled it myself in the end. I just didn’t know what terms to use and you guys provided them in your answers!
Appreciate it!
I would be suppised if there is any city that has a system that delivers centrally heated water to your faucet.
What is done is there is a distinct heating system with warm water that circulates. It will be used in the heat exchanger to heat up cold water delivered to your house to the warm water you get out of the faucet.
The first problem is to have an efficient system that water that is just below boiling temperature. I would be too hot for a hot water tap.
The second is you like to have as clean water as possible in the pipe to avoid corrosion and deposition of solids. It would be costly if you clean water to that degree all the time because people use it. It is also common to have a die in the water so leaks are simpler to detect.
If you turn on the hot water it will likely flow just like in the past but be cold because there is no hot water in the heat exchange that heats it up.
The heating in your house will likely use the district heating system too. It will also use heat exchange and there is no mixing of water.
A heat exchange is simple in that the water is thermal but not physical contact. Take a bucket and fill it with cold water. Then take a metallic pipe that goes into the bucket but exits it to. Let the pipe be a spiral to increase the length of it in the buck. If you pump hot water through the pipe it will heat up the water in the bucket without mixing. There are better designs with more contact are and less waste but they are still just metal that conducts heat between the two liquids, no moving part is needed.
The hole system is water is simply pumped around in pipes with insulation around them. There will be some energy loss in the system but not that much. The pipe looks something like https://sv.wikipedia.org/wiki/Fj%C3%A4rrv%C3%A4rme#/media/Fil:CrNi-Stahl-Wellrohrflex_60_126.jpg
There is a water heater in your home. That large cylindrical thing with a pilot light. Well… if you have one
In the US that is pretty rare. I know a few cities that had steam systems and would pipe excess steam to local schools and municipalities. I have never heard of pumping hot water.
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