Gould Well Drilling Inc/GWDI Laboratory

Regular water testing is essential to keep your water clean and your well operating at peak performance. But many homeowners are stumped when they receive their test results from the laboratory. The often confusing measurements, limits and standards make it tough to determine if your water is safe or if it needs some type of treatment.

Most substances in water are measured as a concentration: a specific mass of a specific chemical within a specific unit of water. The confusing part is that three different terms can be used to reflect the same measurement.

part per million (ppm) = milligram per liter of water = mg/L

part per billion (ppb) = microgram per liter of water = ug/L

So what do these terms really mean? Basically they refer to very small amounts of a substance within about a quart of water (1 liter = 1.05 quarts).

For example: 1 part per million (ppm) = 1 drop in a tall kitchen trash can filled with water

1 part per billion (ppb) = 1 drop in a railroad tanker car filled with water.

These are very dilute concentrations. For example, the government recommendation for sodium in drinking water is no more than 20 ppm; by comparison, the salt content in sea water is 32,000 ppm.

Figuring Out the Standards

The U.S. Environmental Protection Agency (EPA) regulates public water supplies but not private wells or springs. Well and spring owners can use the EPA’s three sets of standards to judge their drinking water quality.

Maximum Contaminant Levels (MCL’s) are the highest level of contamination that the EPA allows in drinking water. MCL’s are legally enforceable for public water supplies; when they turn up in the water, the utility must treat and remove or reduce the contaminant below the maximum level to protect public health.

EPA also sets standards for a second group of contaminants. These limits serve as guidelines for good water quality, but are not required by law. These National Secondary Drinking Water Regulations (NSDWR’s), known as the secondary standards, regulate contaminants that may cause cosmetic effects such as skin and tooth discoloration or aesthetic effects such as taste, odor or color in drinking water. These contaminants are not considered threats to the public.

For example, arsenic (Primary Contaminant) is a naturally occurring mineral found in soil and bedrock. We know that arsenic has been a popular poison in murder mysteries, but the substance also can work its way into ground water through erosion and build dangerous levels in some wells. On most charts, the MCL for arsenic is written as .010 mg/L, what they really mean is 10 parts per billion.

Compare your water test results to the federal standards in the table to assess the potential for health problems.