Homes with wells tend to have their own septic systems, which often leak into the wells. On farms, it turns out, wells are easily contaminated both by nitrates and by pesticides like triazines . Underground and under pressure, water can percolate up, down, or even sideways, allowing contaminants to migrate considerable distances. And once underground water is tainted, it can be decades or even centuries before natural recharging purifies it. As rain trickles through the ground, it does become cleaner.
Wetlands also help remove impurities.
Unfortunately, wetlands continue to disappear at a catastrophic rate, having been ridiculed by politicians. Other large sources of water have become reservoirs for pollution. This occurs as sediments in rivers and lakes retain toxic chemicals from years gone by, and as they absorb new chemical assaults from above. While it is not necessary to spend thousands of dollars on a water system, most experts do not believe that inexpensive water treatment systems are worthwhile for documented problems in your water that may be hazardous to your health. Find out whether you actually have a problem before spending any money on a filtering system.