To harvest rain water or use water from the public water supply – what to do? According to a recent article in the New York Times, which mentions the trouble with the Silver Lake reservoir near Los Angeles California, public water is becoming more and more polluted as time goes on. We covered the problem with the Silver Lake reservoir already – bromates were found in the water. These bromates were due to other pollutants mixing and then being chemically altered by sunlight.
Pollutants are all over the place now. Reservoirs that fill using river water, or surface runoff can have up to 60, 000 different chemicals present in the water, yet only 91 are tested for by law. The above mentioned article states (from a citation using EPA records) that there are more than 60,000 chemicals used in the U.S.
We have already shown, on this blog, and our three other websites, that way less contamination exists in rain water than in surface water, or runoff that comes in contact with areas that have been contaminated by urban development, industry, or agricultural activities. The first few hundred gallons of water that runs off of your roof washes away most of the pollution that has settled from the air. All that is left is the petroleum residue from composition roofing. In the case of non-toxic roofing, such as galvalume, little pollution remains after the initial washing from the first few minutes of a moderate rain shower.
It is important to know that some contaminants need only be present in very small amounts to be hightly toxic over long periods of time (years). Trihalomethanes, Haloacetic Acid, Bromate, and Chlorite and microcystins are some examples.