When domestic water is not supplied by a utility company, it will be supplied by a private well-pumping system that includes a well pump, storage tank, and pressure switch.
As explained in chapter 6, part of the water hitting the surface of the earth as rain, snow, hail, or sleet seeps into the ground and percolates down until it hits an impermeable rock strata through which it cannot penetrate. The water then flows along the strata until it eventually reaches the ocean or a river, which can be more than a thousand miles away. The underground flow is not like a running stream but more like a turtle climbing a rock pile. The water flows through the pores and cracks of rock formations, sometimes surfacing along the way as a river or lake. The water composing this underground flow is groundwater, the top surface of which is commonly called the water table.
Subsurface rock formations that readily yield the groundwater to wells are aquifers. There are two types of wells-shallow and deep wells. A well that draws from an aquifer located less than 25 feet below the earth’s surface is a shallow well. When the aquifer is more than 25 feet below the earth’s surface, the well is a deep well. Wells over 500 feet deep are not uncommon.
Because of the proximity of the surface, shallow wells are vulnerable to contamination from cesspools, malfunctioning septic systems, barnyard manure, and industrial waste disposal. Deep wells, although less vulnerable to contamination, can also become polluted. Bacterial and chemical pollutants move downward in the soil until they reach the water table and then flow with the groundwater. To a large extent, the soil acts as a natural water purifier for bacterial contamination by filtering small suspended solids and allowing large pollutant particles to settle out. In addition, bacterial pollutants tend to die after a period of time; their life spans are usually short in the unfavorable conditions found in the soil.
Chemical pollution of the water source, however, can persist for years. I recently read a newspaper article about a toxic chemical solvent, trichlorethylene (TCE), that was contaminating the water supply of seventeen private wells. The solvent, which is used for thinning paint or removing grease, can cause neurological problems if inhaled or ingested in high concentrations. The source for the contamination could not be determined. The local health commissioner, however, indicated that he thought it was the result of TCE being dumped in the area many years ago, prior to the homes being built.
Water that has a foul taste or odor and appears dirty may be completely potable, whereas water that is very clear and has a good taste may be polluted. You cannot tell by looking at it or tasting it whether the water is contaminated. As a precautionary measure, well water should be analyzed once a year for both bacterial and chemical pollutants. If the house has a well, have the water analyzed prior to contract closing.