Q & A - Water Quality Testing for Private Well Owners

By Krista E. Pearson and Jim Bauder
Montana State University Extension Water Quality Program
Department of Land Resources and Environmental Sciences

What are my responsibilities as a private well owner?
Government or municipal agencies do not monitor water quality in private wells. This means that the well owner is responsible for the quality and safety of the well water. Routine testing for a few of the most common contaminants is highly recommended. Even if you currently have a safe water supply, regular testing can be valuable because it establishes a record of water quality.

All water from natural sources contains dissolved substances. These substances are referred to as primary contaminants when the amounts present are at harmful or problematic levels. Primary contaminants can be biological such as bacteria or viruses; inorganic chemicals such as lead, nitrate or sulfate; and organic chemicals such as insecticides, herbicides, fuel and solvents. Secondary contaminants are not a health risk, but can make water less desirable for domestic use. Secondary contaminants include calcium and magnesium (hardness), iron, manganese, and hydrogen sulfide, odor, taste, and color.

Where can I get my water tested?
Many commercial laboratories in Montana have the facilities to test water. Prices vary but will often be competitive with state labs. When obtaining laboratory services for water testing, look for three things: 1) guidance with collecting samples, 2) analytical services available, and 3) assistance with interpretation of results. An online directory of certified laboratories for Montana and EPA Region VIII (Colorado, Montana, Wyoming, Utah, South Dakota, and North Dakota) is available.

The State of Montana requires certified labs to adhere to the State of Montana Drinking Water Certification requirements which have been adapted from the EPA Manual for the Certification of Laboratories Analyzing Drinking Water. Certified labs in Montana are required to use EPA-approved analytical methods, compile a quality assurance manual in accordance with EPA guidelines, schedule an on-site inspection of laboratory facilities, and perform the accurate analysis of two (EPA) proficiency evaluation samples per year.

What should I have my water tested for?
There is no single test to determine the quality of drinking water and no single test can answer all the questions. It would become costly and, in most cases, unnecessary to test for all possible contaminants. The following table provides guidelines for water testing. It is important to note that an expert should be consulted if you suspect any contaminant that could present an immediate or long-term heath risk.

Table 1. Selecting appropriate drinking water quality tests.
Problem or concern
Water test to consider
Appearance Frothy, foamy Detergents
Appearance Black flakes Manganese
Appearance Brown, yellow, or reddish Iron
Odor or taste Rotten egg Hydrogen sulfide
Odor or taste Metallic pH, iron, zinc, copper, lead
Odor or taste Salty Total dissolved solids, chloride, sodium, sulfates
Odor or taste Septic, musty, or earthy Coliform bacteria, iron
Odor or taste Soapy Surfactants, detergents
Odor or taste Gasoline or oil Hydrocarbon scan, volatile organic chemicals (VOC's)
Stains on fixtures or clothing Red or brown Iron
Stains on fixtures or clothing Black Manganese
Stains on fixtures or clothing Green or blue Copper
Stains on fixtures or clothing Reddish-browh slime Iron bacteria
Stains on fixtures or clothing White deposits, soap scum Hardness (calcium and magnesium)
Uses and symptoms Discoloration of children's teeth Fluoride
Uses and symptoms Gastrointestinal illness Coliform bacteria, sulfates, giardia
Uses and symptoms Water supply used for infants less than six months old, pregnant or nursing women, or elderly with genetically impaired enzyme system Nitrates
Corrosion Pitting of plumbing fixtures and deposits on sinks and plumbing pipes. Corrosivity, pH, lead, zinc, manganese, copper, iron, sulfates, chloride
If you suspect or observe: Leaking fuel tank Hydrocarbon scan, VOC's
If you suspect or observe: Road salt Total dissolved solids, pH, VOC's, heavy metals
If you suspect or observe: Landfills Total dissolved solids, pH, VOC's, heavy metals
If you suspect or observe: Sludge utilization Coliform bacteria, nitrate, metals (lead, cadmium)
If you suspect or observe: Septic system failure Coliform bacteria, nitrate, detergents, total dissolved solids, chloride, sodium, sulfates
If you suspect or observe: Intensive agricultural use Coliform bacteria, nitrate, pesticide scan, pH, total dissolved solids
Table adapted from DeLynn, H. and Skipton, S. 1998. Testing for Drinking Water Quality, G89-907-A.

What are coliform bacteria?
Coliform bacteria are organisms found in soil or vegetation and in the intestinal tract of warm-blooded animals. Coliform bacteria serve as an indicator of the contamination of water and possible presence of intestinal parasites and pathogens. Lab tests for coliform bacteria are relatively inexpensive or can be performed at home using the Coliscan Easygel method. If detected, coliform bacteria indicate that more dangerous pathogens, such as E. Coli, may be present. Therefore, by observing coliform bacteria, the absence or presence of many pathogenic bacteria can be indicated.

How often should I have my water tested?
Generally, private water supplies should be tested for nitrate and bacterial contamination annually. Otherwise, drinking water should be tested if:

Coliform bacteria are most likely to be found during wet weather, when runoff and excess soil moisture carry contaminants into shallow groundwater sources or through well defects. To assess the year-round safety of your drinking water, test for bacteria in the late spring or early summer. Testing during extremely dry weather or when the ground is frozen may not indicate the presence of bacteria because the lack of moisture migration through the soil profile reduces the likelihood of finding high contaminant levels in wells.

Test for other substances when specific contamination is suspected (see Table 1). This might be the result of a spill, backflow, or use of harmful products in close proximity to well or other such event. Any noticeable change in water taste, color or smell signals the need for testing. Collect a water sample at a time when a contaminant is most likely to be present.

How do I collect a water sample?
Laboratories typically provide clean containers and detailed instructions about sampling procedures. The lab should be contacted before the water sample is collected to insure the sample is taken properly. If this is not provided, follow these steps when taking a well water sample:

For best results, refrigerate water samples (DO NOT FREEZE) and have them analyzed within 30 hours of the initial collection. Water samples should be shipped within one day of sampling and on a Monday, Tuesday, or Wednesday to make sure that the sample arrives at the lab in time.

How do I interpret the results?
The Safe Drinking Water Act requires the U.S. Environmental Protection Agency (EPA) to set limits or standards for contaminant concentrations that may pose health risks. There are two categories of drinking water standards: primary (maximum contaminant level) and secondary (secondary maximum contaminant level). Primary standards (Table 2) are the highest allowable concentrations of contaminants based on health considerations. Secondary standards (Table 3) regulate contaminants that cause offensive taste, odor, color, corrosion, foaming, and staining or other offensive or non-desirable conditions which are not necessarily harmful to human health. Although private drinking water supplies are the responsibility of the well owner, these standards can serve as a guide to ensure safe and enjoyable drinking water for private well water systems.

The Montana State University water quality web page provides an interactive lab analysis to help private well owners understand their lab results. Lab results can be entered directly onto the web page and responses about water quality and water treatment are generated.

Table 2. Primary drinking water contaminants.
Potential health effect
Numeric standard (mg/l)
Coliform bacteria Useful as an indicator that other, potentially harmful bacteria may be present
E. Coli bacteria Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)
Antimony (An) Increase in blood cholesterol, decrease in blood glucose.
Arsenic (As) Increased risk of cancer, skin damage, circulatory problems
Barium (Ba) Increase in blood pressure
Beryllium (Be) Intestinal lesions   
Cadmium (Cd) Kidney damage
Chromium (Cr) Allergic dermatitis (occurs after multiple years)
Copper (Cu) Gastrointestinal distress; long term exposure could lead to liver or kidney damage.
Fluoride (F) Bone disease (pain and tenderness), children may get mottled teeth.
Lead (Pb) Delays physical or mental development in infants and children, kidney problems and high blood pressure in adults.
Nitrates Methoglobinemia "blue baby syndrome" in infants under six months - life threatening without immediate attention
Selenium Hair or fingernail loss, numbness in fingers or toes, circulatory problems

Table 3. Secondary drinking water contaminants.
Numeric standard (mg/l)
Aluminum (Al) Colored water
Chloride (Cl) Salty taste
Copper (Cu) Metallic taste, blue green staining
Fluoride (F) Tooth discoloration
Iron (Fe) Rusty color, sediment, metallic taste, reddish or orange staining
Manganese (Mn) Black to brown color, black staining, bitter metallic taste
pH If the pH is low - bitter, metallic taste, corrosion. If the pH is high - slippery feel, soda taste, deposits
(on a pH scale)
Sulfate Salty taste
TDS Hardness, deposits, colored water, staining, salty taste
Zinc (Zn) Metallic taste

How do I treat my water?
Water treatment refers to systems that reduce harmful contaminants in the water and therefore deal with health and safety of the water. High levels of coliform, nitrates, arsenic, lead and pesticides are examples of harmful contaminants that must be treated for water to be safe to drink. Household water treatment processes for common water quality problems are listed in Table 4.

Table 4. Some common water quality problems, causes and cures.
Hardness Soap curd and lime scum in bath, white scale in pipes Excessive magnesium and calcium salts Water softener (cation exchange)
Grittiness Feels abrasive when washing, leaves a residual in bath Silt passing through well screen Sand trap, membrane filtration
Odor Grassy or musty Organic matter Activated carbon
Odor Chlorine Excessive chlorination Activated carbon
Odor Chemical (phenol) Industrial waste seeping into water supply Stop seepage, activated carbon
Odor Rotten egg Hydrogen sulfide Manganese greensand, chlorination, aeration
Taste Salty or brackish High sodium or magnesium content Cation/anion exchange, reverse osmosis, distillation
Taste Metallic Low pH Acid neutralization
Taste Metallic High iron content Oxidation and filtration
Stainless steel corrosion Blackening or pitting of sinks and dishwashers Excessive chloride content Alternative materials, partial reverse osmosis
Turbidity Mud, silt, and/or clay Suspended matter in water supply Filtration
Acid water Green stains on plumbing fixtures Low pH reacting with copper and brass piping and fittings Acid neutralization
Red water Stains dishes and laundry Dissolved iron Oxidation and filtration
Red water Red sediment when water is left standing Precipitated iron Oxidation and filtration
Red water Red color even after standing for 24 hours Colloidal iron Oxidation and filtration
Milky water Cloudiness when drawn Entrained air from faulty pump Water should clear quickly
Milky water Cloudiness when drawn Sledge pickup in hot water heater Clean heater periodicially
Milky water Cloudiness when drawn Methane gas Aeration with proper venting (volatile gas)
Excess fluorides Yellowish, mottled teeth in children Excessive fluorides Activated alumina, reverse osmosis, deinoization, distillation
Nitrates No color, taste, or odor. Possible health hazard for infants. Human or animal waste and/or fertilizers seeping into water supply. Anionic ion exchange, reverse osmosis, distillation, deionization
Heavy metals No color, taste, or odor signs. Possible health effects. Industrial pollution, corrosion products. Softening, deionization, reverse osmosis
Pesticides and herbicides Chemical taste Excessive agricultural spray applications. Activated carbon
Radioactive contaminants No color, taste or odor signs. Possible health risk. Natural radium radioactivity, atmospheric fallout, nuclear waste. Water softening, deionization, reverse osmosis.
Radioactive contaminants No color, taste or odor signs. Possible health risk. Radon gas Aeration at faucet, carbon absorption
Source: Vogel, Micheal P., 1991, Household Drinking Water Protection and Treatment: Montana State University Extension Publication EB 102.

Other helpful extension publications: Montana State Universtiy Extension Publications:

  • Household Water Treatment, EB 84
  • Household Drinking Water and Protection, EB 102
  • Water Quality and Agrichemicals in Montana, EB 51
  • Water "Sense" Diagnostic Wheel, #4404 ($3.95)
  • Water Quality - A Matter of Choice, EB 48
  • Water Quality Testing, Montguide 8418
  • These publications can be accessed online or ordered:
    MSU Extension Publications
    P.O. Box 172040
    Bozeman, MT 59717-2040
    or e-mail orderpubs@montana.edu

    This fact sheet was compiled from the following resources:
    DeLynn, H. and Skipton, S. 1998. Testing for Drinking Water Quality, G89-907-A.

    Donaldson, S., Walker, M. Courtois, D. 2000 Water testing for Private Well Owners.

    Manual for the Certification of Laboratories Analyzing Drinking Water, 1997, EPA 815-B-97-001.

    Vogel, Micheal P. , 1991, Household Drinking Water Protection and Treatment: Montana State University Extension Publication EB 102.

    Waskom, R.M., Davis, J.G, and Self, J.R. 2000. Selecting an Analytical Laboratory.

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    Questions/Comments: waterquality@montana.edu