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We have a large roof-fed rain cistern, approximately 1500 gallons. Make, model, and material were not obvious to me, though I can look harder if needed. It looks similar to this:

It would be nice to use it for collection of snowmelt, as some of our trees need water over the winter. Also, springtime can be very dry here, so I would like to collect in late winter / early spring for use in late spring.

I don't mind if it freezes solid for a while. However, I do mind if it is broken by freezing.

Therefore, my questions are:

  • Do I need to winterize it at all?
  • If yes, when would it need to be winterized? (For example, I could winterize when the average temperature goes below freezing, and un-winterize as soon as it rises above.)

It's in a fairly shady spot in our yard. On the coldest day of the year in our climate (northern New Mexico), the average low is 23°F and the average high is 36. Record low is 6 below. Almost all winter days are sunny.

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  • Unrelatedly, are those pipes protected from UV damage somehow? They look like PVC and standard PVC will become brittle and vulnerable to impact damage in that intense New Mexico sun.
    – iLikeDirt
    Oct 30 '13 at 4:03
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For sub-zero cold climate conditions, polyethylene can get brittle and the disc of ice can expand radially and exert enough force to split it. The usual recommendation is to insulate the tank and provide a heat source such as a submersion heater, heat tape or an earth heat loop buried below the frost line and a circulator pump.

In this case, it sounds like you have solar available, you just have to get warm water to the tank. At 23 degrees, as long as you take care that the pipes themselves don't freeze and the tank is partially full, you might not have that much to worry about. The pipes and fittings attaching to the tank will be the weak points.

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