Water Freezing in Tank
Most recent answer: 01/12/2013
Q:
I want to store 500 gallons of water at my cabin in NM, the winter can be as low as 0 but will warm up to 25-30 degrees during the day when we have a low of zero. I plan on running my main water feed through the storage tank so it always has fresh water in it. We are not there all the time so my question is how long does it take to freeze 500 gallons with temp variation like this? Elevation is 6200
- Wayne (age 61)
Tucson AZ
- Wayne (age 61)
Tucson AZ
A:
It's really hard to estimate things like the rate at which heat will leak out of your water tank. It depends enormously on how well it's insulated. I can make an extremely crude estimate based on the behavior of home water heaters.
A typical home heater holds about 50 gal. The temperature drops significantly (10°C?) over maybe 10 hours or so with a temperature difference to the outside of maybe 50°C. (There's no reason to try to get precise about any one of these quantities since I can't be at all precise about others.) Let's assume that the heat flow is proportional to the surface area and to the temperature difference from inside to outside the tank. Your tank will have ten times the volume, which means about 5 times the area (102/3). Your temperature difference will average roughly 15 °F over the day, or about 10°C. So if you use insulation similar to a home water heater, you'll end up with a heat leak about big enough to cool 500 gal 0.1°C/hr. Freezing water requires removing latent heat equivalent to about 80°C cooling. So maybe freezing the whole tank will take roughly a month. Given the guesstimates, I could be off by a very significant factor here.
If it's not insulated, the time will drop drastically. Also, you may have to worry about pipes, which have much bigger surface to volume ratios and thus may freeze much more quickly.
Mike W.
A typical home heater holds about 50 gal. The temperature drops significantly (10°C?) over maybe 10 hours or so with a temperature difference to the outside of maybe 50°C. (There's no reason to try to get precise about any one of these quantities since I can't be at all precise about others.) Let's assume that the heat flow is proportional to the surface area and to the temperature difference from inside to outside the tank. Your tank will have ten times the volume, which means about 5 times the area (102/3). Your temperature difference will average roughly 15 °F over the day, or about 10°C. So if you use insulation similar to a home water heater, you'll end up with a heat leak about big enough to cool 500 gal 0.1°C/hr. Freezing water requires removing latent heat equivalent to about 80°C cooling. So maybe freezing the whole tank will take roughly a month. Given the guesstimates, I could be off by a very significant factor here.
If it's not insulated, the time will drop drastically. Also, you may have to worry about pipes, which have much bigger surface to volume ratios and thus may freeze much more quickly.
Mike W.
(published on 01/12/2013)