As an electrical and general contractor responsible for building, repairing and remodeling hundreds of homes and commercial projects I tried to stay open to newer and better methods of doing things. At the same time I had to keep in mind the lessons and experiences of the past. A careful melding of this vital information results in a superior product-our home. What we call “green” building and living today may simply be a reawakening to how people lived through necessity hundreds of years ago. Conservation and efficient water use is a good example. No, I’m not talking about carrying a wooden bucket down to the stream for daily water and taking a bath once a year. I am talking about how and why a progressive homeowner might want to consider using a rainwater cistern system.
Why have a rainwater cistern?
Some movie stars and rich people like to tout an alternate way of living. They think nothing of spending thousands to save a hundred as long as they can live “green”–conveniently. The rest of us must conserve and prioritize. Our green projects must serve a viable purpose and/or pay for themselves. Examples could be remote homes with no water service. Water wells are expensive and sometimes there is no water underground. I can’t come up with all the reasons to consider a cistern system, and some good reasons for me are not the same for you. This is an individual decision based on needs, wants and lifestyle.
My particular reason for a rainwater cistern is exorbitant co-op water costs. To be specific my co-op costs twice that of the next lower co-op found in the state of Texas, four times the cost of water in the city less than one half mile away and seven times the lowest Texas co-op cost that I could find. In other words-this pisses me off. A pissed off homeowner is a scary thing to behold.
What does I take to make cistern system viable?
A rainwater collection system and cistern requires rain. As a kid I lived in a desert that received about six inches of rain per year. This was a drought period with an abnormally low rainwater yield but it does happen. Considering a 2000 square foot collection area we could have collected 7480 gallons of water per year. The EPA estimates average water use at 400 gallons a day per household, or a tad over 12,000 gallons per month. Past experience has shown I can get by on 1000 gallons of water a month per person without taking any extraordinary measures. So-the dessert wouldn’t yield enough rainwater, but it could help. I now live in an area that averages 30 inches of rain per year, or slightly over 37,000 gallons of water. Now we’re talking!
Cistern (tank) size for the 2000 square foot rainwater collection system.
Since average rainfall at my home is 30 inches you might divide by 12 and determine that I need a 3,000 gallon cistern. Such a tank is roughly 8′ X 8′. In practice I’d use a smaller 2000 gallon tank in expectation of weekly rainfall and continued water use. I prefer an above ground tank for a variety of reasons. Buried tanks work fine for some people, but I’ve seen too many collapse.
Basic cistern system scenarios
A basic cistern system consists of a collection area (roof), distribution system (gutter, pipes), filter and treatment, and the cistern (tank). A small shallow well pump and pressure tank installed downstream from the tank would complete the installation. The most complicated part of a basic system is the filter and treatment to assure clean, high quality drinking water.
A combination system could include utility supplied water to assist and maintain a certain level of potable water in the cistern.
A cistern and utility supplied water system can be split in any combination of gray and potable water scenarios. This could eliminate the more strenuous treatment requirements for potable water.
This by no means exhausts possibilities for adventurous, frugal, or “green” homeowners. A little thought might reveal the perfect system for your situation. A simple search reveals informative online cistern and stormwater management sites such as Oregon Rainwater Harvesting, Dryland Rainwater Harvesting and cistern plans. There are many more.