Municipal water systems are also users of rainwater. It is just that the water they use has come in contact with and traveled over and/or under the ground. In this process the water dissolves and mixes with all sorts of minerals and chemicals, some are hazardous (pesticides and fertilizers from lawns and farming), and some are just annoying (dissolved calcium chloride and salts) which makes the water hard and leaves mineral deposits in pipes and on surfaces. This raw water is then processed by adding chemicals to treat pathogens and remove some of the hardness. Rainwater collected from your properly constructed system will contain only minimal amounts of minerals. Testing shows no chlorine and a pH between 6.2 and 6.8. All in all the water is very soft; a bar of soap can last for months! All other detergent usage will be reduced as well. Besides, it just feels and tastes good.
Ground water is sometimes heavy in minerals and not desirable in a domestic water source.
Most domestic water waste comes from irrigation of landscaping. It may take 1.6 gallons to flush a toilet, while watering a sizable lawn can take more than 7,000 gallons for a single watering event, with the greatest water demand during the summer when rainfall is sporadic.
The average family of four can use 400 gallons of water every day, and, on average, approximately 70 percent of that water is used indoors.
If you ever experienced this yourself, even for a few days, you would gain a unique respect for the value of water and how you use it. When water comes from a municipal supply the resource appears limitless.
Rainwater collection systems start out as a “large math problem”. Consumption, collectable area, annual rainfall, and storage capacity all contribute to the viability of a rainwater collection system. Size of collection area and maximum rate of expected rainfall will determine which filtering equipment will be needed. Estimated consumption will help determine storage requirements
A general formula that you can use to get an idea of how much water you can collect is:
Inches of Rainfall x Roof Sq. Ft. x 0.62 (evaporation) x 0.95 (Wisy Filter Efficiency) = Approximate Amount of Collected Rainwater
