Well water may contain a variety of impurities beyond simple H2O. Some of these are naturally occurring elements such as Iron, Manganese, Sulphur or Arsenic, that dissolve in groundwater from rock minerals as it passes through the bedrock fractures. Others may be chemicals introduced into the environment by man, such as petroleum distillates, pesticides or herbicides. A third category of impurities are bacterial organisms that may pose health risks, such as e-coli.
There is no one test that covers all possibilities. Water quality analyses are specific to whatever is being tested for. Thus, there is a long list of possible tests that could be performed on a given well.
The presence of bacteria in a well is an indication that water in contact with the surface environment has entered the well. In a new well, it is possible for bacteria to be introduced during the drilling and pump installation processes. It is common practice to chlorinate a new well after the pump has been installed in order to eliminate such contamination. Bacteriological testing of a new well is generally required by the Health Department before the water is certified safe for drinking. (Be sure to thoroughly flush the chlorine out of the system before collecting a sample for testing, otherwise the sample results may be declared invalid).
The continuing presence of bacteria in a well, new or old, after the well has been chlorinated and flushed, is an indication that surface water is somehow entering the well. Commonly this is a result of improper or failed grouting (sealing) of the space between the well casing and the surrounding well bore. In some cases this problem can be fixed by installation of a device called a packer into the well. In some cases it may be necessary to drill another well. It is difficult or impossible to re-grout an existing well.
Mineral elements derived from the rocks through which groundwater flows can affect the pH of well water, the water’s taste, and may cause staining of sinks, tubs and clothing. Knowledge of the geologic setting of the well can be helpful in deciding which elements are likely to be present. Generally elemental impurities can be eliminated through a water treatment system. In order to design the most cost-effective treatment strategy, it is important to have accurate numbers on contaminants that are actually present. Analytical tests for a range of common elements are routinely performed.
Note: many or most of the rock formations in central Virginia, such as granite and gneiss, are made up o f minerals such as quartz and feldspar, that DO NOT tend to dissolve into groundwater. Many or most of the wells drilled into these types of rock DO NOT require a water purification system. While we do recommend a simple grit or sediment filter for all wells, it appears that expensive water treatment systems are being installed unnecessarily (oversold) in some areas.
Environmental contaminants introduced by man can be very hazardous to human health. If a well is located in an area where there are known discharges of hazardous materials, it may be prudent to test for chemical species known to be involved. Some chemicals, such as MBTE, are extremely mobile in groundwater, and have been shown to have migrated considerable distances from the site of a spill. Tests for individual chemicals are very specific, and there is a wide range of cost for such analytical work.