How do they keep water from freezing during the Winter in water towers?
And how do they get water in them in the first place? If you have enough pressure to get water all the way to the top of a building, why not just pressurize the building’s plumbing?
Scupper
You serious or pulling my leg ?
Scupper, if you’re not pulling casdave’s leg, try this link for How Water Towers Work.
As to why the water doesn’t freeze, I’m guessing they keep the water temp above 32 degrees.
Casdave: Well, I never really thought about it. Jeez, make me feel bad, why dontcha?
Okay, I read that article, now I understand and feel like a better person.
For the record, I don’t think that the answer was so obvious that I should feel like an idiot for not knowing it.
Also for the record, doesn’t the “big peach” water tower in that article look like a gigantic bare ass?
Yeah, it does look like a big ass. Here’s another site with unusual water towers.
FTR, I didn’t think your question was obvious. I’m still curious about the OP and exactly how they keep the water from freezing. I’m guessing, without any direct knowledge whatsoever, that it’s a combination of insulating structure and heating systems.
I’d WAG that the water doesn’t freeze for two reasons:
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It’s constantly in motion, being replenished as it’s used up. Water in motion doesn’t freeze as easily.
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It’s not staying up there long enough to freeze; it takes a lake days of subzero temps to freeze, and there’s only a day’s worth of water up there, so it’d run dry before it froze.
Fun cold-weather trivia question #2: Does anybody out there know why the water doesn’t freeze in fire hydrants?
Most fire hydrants in the U.S. are a dry-barrell type, meaning water is not stored in the above-ground portion. Since the water is underground, the temperature remains above freezing. There are also wet-barrell hydrants, which are used only in southern California.
That link to How Stuff Works was interesting, but didn’t answer the question!
Ethilrist answered your question: moving water doesn’t freeze. The water in a water tower is in constant motion. Water is pumped out as people flush toilets and wash dishes; more water is pumped in from the water treatment plant.
I wonder about this. Moving water does freeze, just not a easily, depending on its speed. I question whether the movement cause by usage would be enough to prevent freezing in places like Minnesota.
I think “moving water doesn’t freeze” is a misunderstanding. “Frozen water doesn’t move” would be more accurate. Moving water isn’t frozen because, as you can tell from its liquid state, it’s not cold enough yet to freeze.
I think the other answer must be right - the water in a tower isn’t there long enough to freeze. There is typically only a day or two of water, and the water would take longer than that.
Remember, you have to extract a lot of heat to freeze water - the latent heat is 80 cal/g. If you have a vessel of water and you extract heat energy from it at a rate that its temp will change by 1 degree C per minute, it will go from room temp to the freezing poing in about 20 minutes, but will then take 80 more minutes to freeze (without the temperature changing at all).
Okay, I stand partially corrected.
http://www.hebronindiana.com/archives.htm
http://www.boston.com/globe/search/realestate/hotton/plumbing.htm
http://www.misshomes.com/news/forcesofnature.html
But still, the water inside the water tower is moving, so it doesn’t freeze.
And there’s this. http://www.newton.dep.anl.gov/askasci/gen99/gen99700.htm in which someone asks, “Does water in a water tower freeze?” And the Ask-A-Scientist guy says, “Not usually…it is moving and exchanging too much.”
And there’s the Grand Rapids, Minnesota, water tower.
http://www.pce.com/water/grandrapids_watertower.html
I stand completely corrected – it seems that there is enough movement to keep the water from freezing.
On an unrelated note:
I once lived in an older row home in Philadelphia. The drain pipe from the second floor ran outside the house. One winter, my toilet was running every now and again, causing water to drip down the drain pipe, which eventually froze. They had to use a blow torch to unfreeze it. It just goes to show that normally correct advise can sometimes result in the opposite happening.
Scupper
Don’t take it so hard, I was just funnin 
Actually that link was pretty good, I’m glad you asked.
All of the responses so far have touched on the fact that moving water tends to freeze at a lower temperature than 32F.
Yeah, I’ll admit that the water in a tower moves around quite a bit and probably never freezes and bursts the tower.
But let’s get a little theoretical now. Suppose I have a very long pipe ( say 1" in diameter) filled with water going through it at 1 gallon/minute and initially the temperature is just above 32F. Now let’s cool the pipe to below 32F. Will the water eventually freeze in the pipe? Will it freeze first on the walls of the pipe where the water might not be moving as fast?
Serious replies only, preferably from physicists.
Depending on the length of the pipe, as far as I can tell from my fluid dynamics and thermo and heat transfer, and heat exchanger design references from ASHRAE, yes, it will freeze. But your question is open-ended. How cool is it below 32 F? How long is the pipe? These are critical variables.
And yes, the freezing should start on the walls, where the boundary layer is least turbulent.
I guess us Mechanical Engineers don’t qualify then. :rolleyes:
I work for the local water utility, and where I live freezing is a problem. We don’t have water towers in the usual sense, but about 30 above-ground “reservoirs” in the form of large tanks spread out through the distribution system.
These tanks are made from steel or reinforced concrete, and range from 100,000 gallons to 2.5 million gallons. And we rely on the continuous raising and lowering of the water level inside to keep it from freezing. Yet, some reservoirs still get several inches of ice to form on the surface of the water inside. So they try to increase water utilization from those problematic reservoirs to get more turbulence going.
Also, we have a means of adding heat to the water as it enters the distribution system, although it’s not been used for the last few years (I don’t know why). One of the water treatment plants is located right next to a natural gas fired power plant, and a heat recovery system was built snatch heat from the turbine-cooling water and warm up the water in the distribution system.
Also for the record, doesn’t the “big peach” water tower in that article look like a gigantic bare ass? **
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Yeah, and then there’s that little “protrusion” at the bottom!
Q