We're planning to buy a smallish above ground pool next year, to please the kiddies, then for water storage after September.

We talked about the freezing issue, many of the big above grounders around here freeze solid.

What if in addition to the standard issue blue pool cover, we put a big black tarp on top? I thought maybe it would keep the average temp of the water much higher than otherwise, and avoid the really big ice cube...

Whatcha think? We are also going to harvest rainwater; been thinking black barrels might be best...

-- Arewyn (nordic@northnet.net), November 13, 1998

Answers

We have a 20 ft above ground pool. When it was first installed, it was dug it in about a foot overall. Then another foot deeper in a concave center that starts from a circle about 2 ft in from the walls. The flat liner stretches to fit very nicely. We did this for the nicer appearance that a lower silhouette offers and of course the center was dug for the greater depth. The curved deeper bottom makes for a nice dive line. Another thing we have done is to enclose the outside in styrofoam insulation. The eight sides of the pool are covered by 2 x 8 ft. pieces of solid foam boards that were caulked to the aluminum walls. Caulking around the edges also keeps air from circulating beneath the insulation. The wall is covered from the ground up to near the waterline, with the lower foot of the wall being underground. The foam board has a nice white textured surface and being protected by the the walkaround deck above, it doesn't get damaged, even though its sort of fragile.

This was done to keep our pool warmer longer in the fall but it turns out that our pool never freezes entirely. The ground below keeps it from going that cold. Although I don't believe it did even before we put on the outside insulation, I'm sure that it helps now that its there. The surface freezes to perhaps a foot but the rest remains fluid. We figure we can chop through and siphon off any amount we need for washing, flushing, etc. during the entire winter, as (and if*) needed. *I try to keep a little optimism. :-)

BTW; we have always had black liner on the surface during the winter. That's just the color it happened to be made in but, now that I'm thinking about it, it would certainly be inclined aid heat retention by soaking up the sunlite.

Me

-- Floyd Baker (fbaker@wzrd.com), November 13, 1998.

Very good idea about the insulation around the sides.

-- Robert A. Cook, P.E. (Kennesaw, GA) (cook.r@csaatl.com), November 13, 1998.

Robert may correct me but i supect that the best color would be a dark, dark (Coleman) green. I say coleman because the color I'm referring to is the color they used to make their coolers out of, until they realized that the trademark color was an error.

This dark green is the best color for collecting the sun's energy and NOT re-radiating back. It happens to be the color in the exact center of teh sun's radiation spectrum. Or so I was told long ago. Another problem is that, while black is the best all around energy absober, it is also the best all around energy radiator.

C

-- Chuck a Night Driver (rienzoo@en.com), November 13, 1998.

PS One assumes that you have been watching the threads (several, on Pools) here that have concluded that the water will probably not be potable but GREAT for washing and flushing??

c

-- Chuck a Night Driver (rienzoo@en.com), November 13, 1998.

Ref: radiation. True. Black (flat, soft or non-glossy - whatever term you like) is best at both "directions" of reflection. The back (lower) surface of the black cover will be more effective at radiating warmth down too. A "hard black" will reflect some of thewarmth you want to retain - but obviously the lighter the color, the glossier the finish, the more energy is reflected from the upper (sunny) surface.

However, reflected light (heat) is slightly shifted in the process. So try a "greenhouse effect" to increase insulation, "trap" the re-radiating warmth from the upper surface of the black/dark green cover, and to keep the black surface clean - and so more effective.

So let us imagine this "greenhouse" pool configuration:

Upper surface of clear (not translucent (?), moderately heavy) plastic relatively tight (flat perhaps, or slightly "domed" in the center to shed water and reduce snow/leaves buildup) . If the "dome" is too high, the trapped air will convect and cool over night and retain little heat energy. Under that, a flat black (existing) cover, or new dark green (as mentioned) cover) over the water.

Styrofoam or wrapped (covered) fiberglass insulation (2-3" batts) around the sides, covered with a simple protective sheath of plastic to keep off wind/water damage. Underneath? As-as probably, if already on the ground. Else, isolate the bottom (On a deck? Try to trap the air below, consider adding some insulation below the deck.)

-- Robert A. Cook, P.E. (Kennesaw, GA) (cook.r@csaatl.com), November 13, 1998.