We built our rain harvester because we needed more water if we wanted to grow our vegetables to their fullest potential and feed ourselves year round. We live in a big old house that's broken up into a few apartments; altogether, there are six people who live here. Since it's an old house, we've got a well rather than city water. And since we're just up the street from a quarry, the well is shallow. Our landlord lets us do whatever we want on the house's three and a half acres of land with only one restriction: we can't use the hose. So for us, some sort or rainwater collection system was a necessity. We also plan to collect water when we build our own house (that'd be future house) and wanted to take the opportunity to build a practice rain barrel system.
Before we built the rain harvester, we were collecting a minor amount of rainwater via a garbage can wedged under a downspout. This gave us enough water to triage the thirstiest plants and keep seedlings from drying out, but it wasn't fun to make repeated trips though the yard hauling the watering can, and it was a mosquito nightmare. It also severely limited the size of our garden. We wanted to grow a lot of stuff, but with only 55 gallons of water in reserve a large garden was too much of a gamble. Our corner of Pennsylvania usually gets a decent amount of rainfall in the summer at fairly regular intervals, but that's never something to bank on.
When we started seriously thinking about how we could collect water, we came up with a list of requirements to design our system around. We wanted to be able to store a few hundred gallons of water so that we could water our vegetables at least a little bit in the event of an extended drought. We also wanted something relatively cheap: huge cisterns and pre-built barrel systems were out of the question. And because we don't own the house or the land, we didn't want the rain harvester to be a permanent fixture.
So. We decided on a PVC and barrel setup that could be extended in the future. I think similar systems would work for most people because they're cheap, simple, and can be kept fairly small. If you're looking to collect rainwater, here are some things to think about:
- How much water do you need? Take into account the size of your garden, the water needs of your plants, the typical rainfall for your area, and any plans you might have for expansion. If you grow only a few vegetables or just want enough water to keep your flowers happy through the summer, one or two barrels will probably suffice. If you live in an extremely dry area and want to capture as much water as you can, more barrels will obviously be better. In our case, we get a decent amount of rainfall but our 1200 square foot vegetable garden needs a bit of extra insurance, so we went with a system that keeps nine 55-gallon barrels full most of the time.
- How much water can you collect? In addition to your area's rainfall, this depends on the amount of area your roof covers. The formula for figuring out how much water your roof can catch is: G = 0.416AR, where G stands for gallons, A is the area under your roof, and R is rainfall. For example, if you want to figure out how much water the roof of your 20x25 foot garage will catch if you get an inch of rain, you'd do G = 0.416(500)(1), and find that you'll get 208 gallons of water. Nifty! This can help you determine how much storage capacity you need.
- Where is your garden relative to your house? Thinking about this can help you to figure out how to situate your rain harvester. Our garden is downhill from our house, so we can rely on gravity to carry the water through our hose. If you're working on flat ground, you may need to elevate your barrels a good deal to produce water pressure. On a related note:
- Are you willing to supply power to a water pump? If you need very strong water pressure or if your water needs to travel uphill, it might be necessary to hook up a water pump to your system. We wanted to avoid using power for ours, and we were lucky that our slight downhill pitch gave us enough pressure to use a hose in the garden.
- What's your budget? You can build a small 100 to 200 gallon system for under $50 and expand it later on. Ours holds about 500 gallons and cost us around $175. It also can be expanded. It's possible to do the same thing for quite a bit cheaper, too—we bought our barrels, but it wouldn't be very difficult to get some for free. We'll get into a specific breakdown of costs in a later post.
And that's the gist of it. We did a lot of planning before we bought any materials, and because of this I think we were able to build a pretty good system. Anyone thinking about collecting rainwater should really think about their needs before making any investment; different circumstances will lead to big differences in water collection systems.
That's quite enough of us for one day. We've got three more posts about our rain harvester in the works. Tomorrow we'll write about different kinds of collection vessels and how to get your hands on them. On Tuesday we'll run through all the materials we used and how we put everything together, and on Wednesday we'll discuss how the whole thing works and how to take care of it. In the meantime, you might want to check out the comments on this recent Garden Rant post, where a number of people shared their water collection requirements and ideas.