Gi'day from Australia Wild Garden !
Well, you certainly have done your maths !!!
However you might like to check out the pre-made water tank options before you attempt to build your own. The engineering complications of what you propose can be enormous due to the stresses that amount of weight and mass can produce. You can see some of our 5 tanks( 1x 10,000 gal,2 x 5000 gal,1x4000 gal and 1 x3000 gal= 27,000 gallons)at www.ozbushandbeach.com under "photos of the bush property" to give you an idea of the kind of water storage we require in the aussie bush !! We also have a large lake which is not very large at the moment for irragation. What part of Virginia are you in ?? I went to collage in Blacksburg many years ago.Paul

Hi wild_ garden! That's a wild idea. I know what you mean about Va being bone dry, seems all the rain misses me here in the middle but the southside gets the storms of late. I've been grinding my head gears too about the better ways to store water. Just bought a country home that has about 10 downspouts on it and am considering digging a below ground cistern and leading all the runoff into it. Be a lot of work laying the underground lines but they could be connected together by one larger pipe leading to the cistern. Would need to incorporate a pump since gravity is of no help as it would be with your above ground system. Also, when it's this dry there's no rain to refill it so it'd have to be extra large to catch the winter rains for later use. Ahhh, so many ideas, so little time. But it's either this or shell out $5K for an artesian well dig :o(. Good luck with you dream, vgkg

You will have to reinforce the walls of the cistern, perhaps by a bolted-on frame of 2x4s, or have a LOT of dirt piled into a sloping walls oif the cistern, Water is HEAVY, and the outward pressure at the base will be considerable.

What would 4 500-gallon stock tanks cost?

Or, one of the 3 foot swimming pools that sell for a little under $200. You can cover it to keep evaporation under control. I think one of the 3 ft.x 12 ft. holds about 8,000 gallons to keep stability for swimming, probably more for water storage.

You can get water storage tanks of polyethlene from any farm supply, a 1500 gallon tank is roughly 7 feet around and 5 feet tall, last time I looked they sold for around $600...Bob.

aussiebuffer// i'm out in the shenandoah valley i know where blacksburg is and have visited there many times! nice area, very pretty country.

lazygardens// the 4x 500 gallon tanks would cost 4x 528$us from http://www.tank-depot.com/, i'm sure they could be found cheaper. total though that's about 2k$us.

vgkg// check out getting a single solar panel to run your pump! when the sun is shining your pumping water for "free" (nevermind the 500$us cost for a 100 watt solar panel lol).

on the comments about the above ground liner based storage tank needing a lot of dirt to hold the water, well, yeah, that's what i said too lol. sure you could use wood to reinforce it, or rocks, or mortar a few courses together or all kinds of things. i thought that was the cheapest and easiest solution until ...

frieda has the cheapest solution so far i think, if you can purchase a pool that is 3 feet deep by 12 feet across (6 foot radius) then that'll hold 339 cubic feet of water or about 2500 gallons for 200$us. where do you get a pool that big for 200$us frieda ? i mean 3 feet deep and 12 feet across that isn't one of those plastic kiddie pools lol.

You can buy the above ground pools from Sears, and Wall Mart different sizes $5oo. and lower they come with a small filter. The filter recirculates the water in normall use. Instead of recirculating the water back to the pool use the filter and some conncted hoses to pump the water were you want it, or use some kind of siphioning hoses. When it does rain refill the pool with the rain from rain gutters.
Lindag

whatever did happen to cisterns, anyway? when i suggested this to my husband, i got the old eye-roll. why not run your rain gutters to a cistern under the deck- so many new and old houses have decks now, and there's nothing under there but the neighborhood skunks and groundhogs!

Cherylm, I certainly hope that blankity groundhog hasn't found my deck. It surely can't cause it can't even find my trap. A cristern under the deck would be a great idea if it doesn't create problems with the deck supports. From the experiance of digging a basement out from under my house I don't think I'll be putting in a cristern under any deck. Digging under any thing lower than standing height is not fun work.

Here is a price for a kiddie swiming pool
http://www.patiostore.com/Poolstore/sunpool.html
Size: 9.83' x 6.56' x 2.46'
Holds 1189 gallons
Steel Frame
Equipped with Drain
See feature section above
Reg $359, on sale $249
The Summer Sun 300 is huge, almost 9.83' x 6.565' x 2.46' deep. Standard with an extra heavy, nylon re-enforced vinyl liner and powder coated steel support frame. For the small yard or when a full size pool won't do, the 300 is the answer. The Summer Sun 300 is much larger and deeper than typical blow-up pools. A longer lasting and hassle free alternative to the small metal wall pools.

It is possible to put together a concrete block cistern and seal it with cement, or if you are in an area where the weather is very warm and very dry, BlueMax sealer will work. We tried the bluemax but it did not work because of high humidity, and low temps. Fill the blocks with cement and cover the inside with at least 6 coats of Portland cement. Once the cement has set, it just gets harder under water. There is a cement that is ok for potable water, it is listed at the website I have linked to here in this post. All the info is in the link. Be aware that lots of portable swimming pools have sterilization chemicals embedded in the plastic, which make the water non-potable. Also, be aware that water is very, very heavy. The concrete block cistern we built holds about 2500 gallons of water, which weighs close to 10 tons (20,000) pounds (that's not including the bricks or concrete!)

Here is a link that might be useful: concrete block cistern