# hot water in apartment **URL:** \ **Category:** Factual Questions\ **Created:** [February 19, 2015, 9:40pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133 "2015-02-19T21:40:51Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![stosh](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@stosh](https://boards.straightdope.com/u/stosh)\ **Post date:** [February 19, 2015, 9:40pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/1 "2015-02-19T21:40:51Z")
Hi Guys, I live in a 85 unit apartment building and for the 4 years I have been here I have never run out of hot water. I wonder what kind of hot water heater they must have. Any ideas ? ---
**Author:** ![Lanzy](https://avatars.discourse-cdn.com/v4/letter/l/74df32/32.png) [@Lanzy](https://boards.straightdope.com/u/Lanzy)\ **Post date:** [February 19, 2015, 9:47pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/2 "2015-02-19T21:47:56Z")
More likely a boiler than a water heater. I’ve never run out of hot water on a cruise ship either. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [February 19, 2015, 9:50pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/3 "2015-02-19T21:50:04Z")
They probably have more than one. ---
**Author:** ![Doug\_Bowe](https://avatars.discourse-cdn.com/v4/letter/d/df788c/32.png) [@Doug\_Bowe](https://boards.straightdope.com/u/Doug_Bowe)\ **Post date:** [February 19, 2015, 9:50pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/4 "2015-02-19T21:50:41Z")
Ask the Super. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [February 19, 2015, 9:59pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/5 "2015-02-19T21:59:24Z")
Large buildings like hotels and large apartment buildings like that usually have a boiler combined with a constantly circulating hot water system. Instead of the hot water just sitting in a tank somewhere like it does in your home, the heated water is constantly circulated through the pipes in the building. That way, not only is there always enough hot water for everyone, but there’s also no delay between when you turn on the hot water faucet and when the hot water actually comes out. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [February 19, 2015, 10:03pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/6 "2015-02-19T22:03:02Z")
I have lived in numerous houses with lots of other people and have never run out of hot water. My guess is that they sized their hot water system so that everyone could be drawing from it at the same time and they still wouldn’t run out. Since it’s rare that everyone **is** drawing from it at the same time there should be plenty for anyone who needs it. Have you ever tested this? Have you left the bathtub filling with hot water, with the drain open of course, and verified that after an hour, two hours etc. it doesn’t run out? Not that anyone would take a 2 hour shower… ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [February 19, 2015, 10:25pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/7 "2015-02-19T22:25:06Z")
It’s not always just the sizing of the water system. There are different types of hot water systems for homes. My home has a boiler furnace which supplies the hot water for the house as well as for the baseboard water heating system. There’s no water storage inside the furnace (other than whatever water is inside the heating coil at the time). The water is heated on-demand. I could turn the shower on and leave it on pretty much forever and never run out of hot water. The furnace is sized to heat the entire house plus whatever water we can draw from it. It has absolutely no problem keeping up, though the hot water temperature does drop a litle in the dead of winter when the heat is on full at the same time that you are taking a shower. It’s still plenty hot for a shower though. I also have to warn people that I don’t have warm water, I have hot water. Folks get used to setting the thermostats down on their water heaters to save money, and then they can crank the hot water on full and won’t burn their hands. If you turn on only the hot water in my house you will burn yourself. There are also tankless systems that aren’t boiler furnaces but basically do the same thing, heating the water on-demand as opposed to storing it in a tank. Those systems also don’t run out of hot water. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [February 19, 2015, 11:16pm UTC](https://boards.straightdope.com/t/hot-water-in-apartment/713133/8 "2015-02-19T23:16:42Z")
> [@engineer\_comp\_geek](#): > > I also have to warn people that I don’t have warm water, I have hot water. Folks get used to setting the thermostats down on their water heaters to save money, and then they can crank the hot water on full and won’t burn their hands. If you turn on only the hot water in my house you will burn yourself. you should install a thermostatically controlled mixing valve on the domestic hot water coming out of the boiler, it mixes cold water (if needed) to keep it at a safe temperature. i have solar thermal preheat tanks going into my hot water heater. because on a real sunny day i could be putting scalding hot water into my hot water heater (indirectly heated from a boiler and thermostatically controlled) and distribute that to my house, there is a mixing valve on the outlet of the hot water tank.