Thursday, March 26, 2009

Rainwater Catchment

This is one of my spring 08 projects. I've always wanted to do rainwater harvesting, and 2008 was my year to do it. I bought a 1000-gallon plastic tank from Western Blend, located on Valley Drive north of Las Cruces. With tax, the tank cost me $699.19, and they delivered it for free.

I built a heavy-duty platform, since a full tank of water weighs over 8000 pounds. I used railroad ties for the uprights, digging holes and embedding them in concrete. You get a massive amount of lumber for the price, but I vowed never to buy railroad ties again. Not only are they extremely heavy, but they are embedded with sand and gravel, which quickly dulls the chainsaw blades I was cutting them with. I was able to get a couple of cuts per chain, if I was lucky. Fooey on that; if I ever do something like this again, I'll just buy treated 6x6 lumber and pay the higher price.

For the horizontal part of the platform, I used treated 2x8 lumber on 12" centers, and on top of that I nailed treated 2x6 planks.

I'm currently harvesting rainwater from the roof to the right of the tank; that's my honey extractor visible through the window. This summer I hope to add a gutter to the room on the left and harvest from that roof as well. The brown pipes are to handle the overflow. Two 4" pipes is probably overkill, but I wanted my system to handle any 4" rains in the future, God forbid.

I had planned on drip irrigating a small garden with this tank, and I might still do it. One thing to consider is that we can easily go 9 months or more between rains heavy enough to fill a tank, so it would be very easy to empty a tank and still have months to go before the next rain. For this reason, I'm using our stored rainwater to irrigate houseplants, and fill the fish tank -- they appreciate the relatively pure rainwater rather than the alkali-laden river water or worse, well water.


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