Back to the Garden Art page.
Back to the Blog 2007 page.
After losing five important trees to the 2007 drought, the threat of another rain-free summer meant it was time to make a decision about collecting rainwater. Al Cooke, the Chatham County Ag Agent, assembled an extensive list of links about rain collection at Rain Harvest. The page offers a lot of things to think about when designing a system, as well as links to many many other sites about rainwater collection. This article is a record of the process we followed to get our system up and functional.
Plenty of websites discuss the issue of "How much can we get?" Allow 600-700 gallons per inch of rain, per thousand square feet of ground-floor house. This is a lot of water. It doesn't take much rain at all to fill a barrel or two.
This datum leads to, "how much water do we (think we) need?" which leads almost immediately to, "how much can we afford to store?" (We'll come back to "How much do we need?" later.)
Collecting and storing water is an expensive proposition. At $10 each, a garden-safe plastic 55-gallon drum provides water storage at $0.20 per gallon. Add plumbing (collection cup, faucet, overflow, connector to another barrel) for $15, and the price of water has risen to $0.45 per gallon.* Pre-packaged barrels sell for $50-$95, plus shipping in some cases, and store between 55 and 80 gallons of water, at a cost of $0.90-$1.20/gallon. I pay less than a penny a gallon for water from the county.
*Once you know what parts are needed, you may be able to find them cheaper. We just picked up two collection cups at the Habitat resale shop for $1.50 each vs. $5+ new. Until we'd built one collector, however, we wouldn't have known which parts were a bargain and which were a waste.
However, in August when the county has imposed water use restrictions and expensive trees are showing signs that they're not going to make it, the relative cost of water changes. Fines. Replacement trees. Dead tree removal. Lost years of landscaping growth, and the thought that next year's summer may not have any more rain, so replacement trees will die, too. All of a sudden, $0.45 for a gallon of landscaping water doesn't seem so bad. Furthermore, the cost of barrels is a one-time charge; they'll collect water for a long time. And rainwater itself is free.
It quickly becomes obvious why farmers store water in ponds. It's the cheapest way to store thousands of gallons. (In most cases, pond storage will require a pump to deliver the water where it is needed, so the cost per gallon equation gets complicated.)
Dig a pond if it's an option. If it's not, read on.
If you can reduce the cost of the storage system at all, the storage cost falls rapidly. Our system uses one "collection" barrel per downspout, built with a PVC collection cup to accept water from the downspout and a brass faucet that will allow us to get the water out of the barrel into the garden. We move the water from the collection barrel to "storage" barrels using threaded galvanized pipe and irrigation tubing. Because the inlet and outlet plumbing is the most expensive, a storage barrel only costs $13 or so, rather than $25. We will be able to connect as many storage barrels as we want; our town does not have appearance restrictions.
Piedmont Biofuels Co-op sometimes sells 375 and 250-gallon intermediate bulk containers (IBCs) (square plastic container housed inside a welded aluminum frame) for $100. They did not have any in stock when we started building our system.
I'd like to have at least a 700-gallon capacity, which means we need 14@55-gallon drums. Any brief thunderstorm would help to recharge the system, turning what would normally be water that runs off baked earth into drip irrigation that soaks in deeply.
At some point in a hard summer, decisions will need to be made about which plants get the water. You may not be able to save everything. Thinking about which plants are most important to you is part of the design of the system.
Consider the relationship of the downspouts to the areas of the garden that will get the water. In my yard, all of the important plants are lower that at least one or two downspouts, but all plants are not lower than all downspouts. If this thinking indicates you will need to move water uphill, you will have to look elsewhere for suggestions. Our system was designed to be pump-free.
I have a ranch house with single-ridge roof. The yard slopes steeply along the short axis of the house, enough so that I have a walk-up basement entrance in the back. I have five downspouts, one at each corner of the house and one at the edge of the front porch roof. The trees that matter to my landscaping are in the front yard, and I also have blueberries, grapes, and blackberries in the backyard that would benefit from additional water. There are no covenants or restrictions in this part of the county about what I can do, appearance-wise, with rain barrels.
ADD PICTURE HERE. After a few false starts, we decided to collect water in three separate systems, one each at the south, southwest, and north corners of the house. The slope and landscaping at the northeast corner are such that collecting water there may kill the camellia growing next to the downspout (wrong plant, wrong place, but I'm not going to kill a 50-yo camellia just to get a little more rainwater).
We studied all the pictures on the how-to-build-a-rain-barrel sites and thought about the hardware we would need and decided to try one barrel first. We connected it to the most accessible spout. Turns out that the spigot screws into the barrel just fine; feels firm, doesn't appear to need interior washering, and doesn't leak. In time, it may be a good idea to get the spigot off the barrel, so that pressure on the handle doesn't weaken the plastic barrel. That's a future problem. (WRONG: A spigot screwed directly into a plastic barrel without any inside support will last for 3.5 uses. On off on off on off on OUT OF THE BARREL. We plan to run tubing from the hole in the barrel to a spigot which will be attached to a rigid support, probably the board on which the barrels rest.) A few rainfalls and the barrel was full.
Once we saw what it took to get the water from the downspout into the barrel, we had to rethink our initial design. In the catalog pictures, the barrels sit neatly under the downspout, which runs directly into the barrel. These people do not have electric meters. Or camellias. Or sloping cut-away land right under the downspout. For today, we're using flexible downspout extenders, mostly because I already owned them. I would like to build PVC connectors in time, but that can wait a bit while we figure out the details. PVC gets expensive, comparatively.
For the second implementation, we addressed the north spout, and this time tied two barrels together. Rather than taking the water around the corner to the driveway, we decided to store it right in the front of the house.
Gravity 2: water is heavy, and plastic deforms under pressure. The base of the barrel must be fully supported or the weight of the water will deform the plastic, perhaps past the breaking/leaking point. We raised our barrels on concrete blocks and 2x10x10 PT lumber. Some barrel vendors sell stands. Up goes the storage price…
Gravity 3: water seeks its own level. If you're daisy-chaining storage barrels (without valved connectors), they will either all be on the same level, or you'll only store the amount of water between the bottom of the highest barrel and the top of the lowest. We plan to connect at least six barrels to the two downspouts at the north corner of the house, which between them collect 2/5 of the roof area. Leveling the support for these barrels, amid the roots from two azaleas, a camellia, and a hunking patch of Virginia creeper vine, turned out to be a non-trivial problem. Water from these barrels will be used on the dogwoods and crape myrtles in the front yard.