University of Maryland Extension

Water Quality and Testing

According to the EPA, actual events of drinking water contamination are rare, and typically do not occur at levels likely to pose health concerns. However, drinking water can get contaminated from naturally occurring sources in the environment or through human and animal activities. Some possible sources of contamination include:

  • septic systems,
  • underground fuel tanks,
  • landfills,
  • industrial spills or discharges,
  • animal wastes, fertilizers, and pesticides, and
  • prolonged periods of heavy rain.

Who Should I Get to Test My Water?

We recommend using a lab that has been certified by the MD Department of the Environment (MDE) to provide water tests. MDE updates their list of certified labs every year. We have pulled out the labs that provide testing services for private well owners, which you can access here.

What Should I Test For? 

If you have not tested your water in several years, we recommend getting a comprehensive test that includes the following contaminants (* indicates those that are of particular concern for pregnant women, infants, and young children):

  • Total Coliform Bacteria*
  • Nitrate*
  • pH*
  • Lead*
  • Copper*
  • Sulfates
  • Total Dissolved Solids

You should also contact your county well permitting office to check for any additional contaminants that may be of local concern. Once you have tested your water, you should continue with routine tests as follows.

How Often Should I Test?

ANNUALLY: Test for coliform bacteria and nitrates. 

EVERY 3 YEARS: Test for pH, Total Dissolved Solids, and Sulfates.

You should also test your water if:

  • You have a pregnant woman or infant residing in the home,
  • Your family or guests experience unexplained or recurring gastrointestinal illness,
  • Your neighbors find a dangerous contaminant in their water,
  • Your suddenly changes in taste, odor, color, or clarity,
  • There is a chemical or fuel spill into or near your well, or
  • When the well system has been repaired or parts have been replaced.

Once you receive your results from a water testing laboratory, simply enter those values into the appropiate boxes on the website below to get an interpretation of your results.

Want to Know More About the Contaminants?


What is it?

Health Effects

Total coliform bacteria

Bacteria that occurs naturally in the environment and is found on the soil and in vegetation; General indicator of water quality

May cause gastrointestinal distress


Compound found in fertilizer and manure

Shortness of breath; Blue baby syndrome in infants under 6 months; Health risk to pregnant women


An indicator of the water’s alkalinity or acidity

Not harmful to human health, but depending on the value, the pH can affect the taste and feel of the water, damage plumbing, and potentially leach dangerous metals from pipes and fittings


Metal that acidic groundwater can leach out of plumbing, pipe materials, or lead solder or brass fittings and components

Irreversible damage to the brain, kidneys, nervous system, and blood cells; Irreversible developmental effects make children, babies, and fetuses most susceptible to lead poisoning


Metal that acidic groundwater can leach out of plumbing, pipe materials, or lead solder or brass fittings and components

Gastrointestinal distress; Liver or kidney damage


Naturally occurring compound in groundwaterHigh levels may cause diarrhea, causing dehydration that is especially detrimental to infants and young animals

Total Dissolved Solids

General indicator of water quality; Measures dissolved impurities

Not harmful to health; High levels may affect the water’s taste


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