I have been harvesting rainwater for several years here in Los Alamos, and I know many other people have been doing the same.
Before investing in a system to do that, it’s worthwhile to run the numbers. First of all, we have about 18 inches of rainfall annually in Los Alamos. For a typical home, that translates into about 20,000 gallons of water that hits your roof every year.
A standard water sprinkler puts out about 5 gallons a minute. I water my garden for about half an hour every other day. That’s 150 gallons per watering. I would like to store enough water to get through May and June, so need about 4500 gallons of water storage. That’s easily doable just by taking water from your roof.
I have an extra bonus in that I have a couple of pools in the arroyo behind my house that hold about 3,000 gallons. To get the storage levels that I would like, I have a 1,500 gallon water tank as well.
Here’s the rub. That tank cost more than $800. It holds about $5 worth of water at the county rate. That means that you would have to fill it 160 times in order for it to pay for itself. I fill it once a year. So, unless you can buy a used tank for about 10 cents on the dollar, this isn’t going to be a money saver.
Fortunately, cost isn’t the only consideration here. Tap water in Los Alamos is pretty alkali and it doesn’t grow things very well. Rain water works a whole lot better. Since I am watering a vegetable garden, I think the investment is worth it.