Drinking Water Quality: Testing and Interpreting Your Results

• Bacteria
• Routine water analysis, including:
  • Conductivity
  • Magnesium
  • Manganese (total)
  • Sodium absorption ratio (SAR)
  • pH
  • Sodium
  • Nitrates
  • Total dissolved solids (TDS)
  • Calcium
  • Iron (total)
  • Hardness

Each year, general indicators, including:

• Bacteria, pH, nitrate and total dissolved solids
• Any constituents that were at or near the drinking water standard in previous years

• Comprehensive water analysis
• Routine water analysis, plus
  • Potassium
  • Alkalinity
  • Chloride
  • Fluoride
  • Sulfate

Note: Keep copies of all results so you can track changes in your water quality through time.

A sterile container provided by the testing laboratory is required for a bacteria test. Check with the laboratory for sampling and timing instructions because samples must reach the lab within 36 hours. Do not to rinse containers because most contain preservatives.

A “raw” water sample is preferred for a routine water analysis. If possible, bypass water treatment units, such as water softeners, reverse osmosis (RO) systems and iron removal systems, when collecting the sample. A second sample taken after the water has passed through the treatment equipment will help you determine if your equipment is functioning properly.

Give special attention to contaminants that have tested high in the past or when concerns arise from health issues. Use a clean plastic or glass container to collect a 1-quart sample. Containers previously used for bleach, soap or other substances will contaminate the water sample. Rinse the container and lid three times with the water that will be tested. Laboratories recommend samples reach them within two weeks.

If you are concerned about water quality due to present or future oil activity, a list of suggested tests is available in NDSU publication WQ1614, Baseline Water Quality in Areas of Oil Activity or through the laboratories later in this article.

Alkalinity is a measure of the capacity of water to neutralize acids. The predominant chemicals present in natural waters are carbonates, bicarbonates and hydroxides. The bicarbonate ion is usually prevalent. However, the ratio of these ions is a function of pH, mineral composition, temperature and ionic strength. Water may have a low alkalinity rating but a relatively high pH or vice versa, so alkalinity alone is not of major importance as a measure of water quality.

Alkalinity is not considered detrimental to humans but generally is associated with high pH values, hardness and excessive dissolved solids. High-alkalinity waters also may have a distinctly flat, unpleasant taste. Treatment is an ion exchange via the addition of a tank media or reverse osmosis.

Arsenic is a semi-metallic element that is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth, or from agricultural and industrial practices.

According to the EPA, long-term exposure to arsenic in drinking water is linked to cancer of the bladder, lungs, skin, kidneys, nasal passages, liver and prostate. Noncancerous effects of ingesting arsenic include cardiovascular, pulmonary, immunological, neurological and endocrinal (for example, diabetes) problems.

Treatment depends on the level of contamination. Typical recommendations include the addition of an anion filter or tank media.

Refer to the list of publications later in this page for more information on filtration.

Calcium and magnesium are the main contributors to water hardness. When water is heated, calcium breaks down and precipitates out of the solution, forming scale. Maximum limits have not been established for calcium. Magnesium concentrations greater than 125 mg/l may have a laxative effect on some people. A standard softener, reverse osmosis or distillation can be used to remove calcium and magnesium from water.

High concentrations of chloride ions can cause water to have an objectionable salty taste and corrode hot-water plumbing systems. High-chloride waters have a laxative effect for some people. An upper limit of 250 mg/l has been set for chloride ions, although noticing the taste at this level is difficult, and even higher concentrations do not appear to cause adverse health effects. An increase in the normal chloride content of water may indicate possible pollution from human sewage, animal manure or industrial wastes.

Color may indicate dissolved organic material, inadequate treatment and high disinfectant demand, and may indicate the potential for the production of excessive amounts of disinfectant byproducts. Inorganic contaminants, such as metals, are also common causes of color. In general, the point of consumer complaint is variable, ranging from 5 to 30 color units, although most people find color objectionable in excess of 10 color units. Other contaminants that may be related to change in water color include aluminum, copper, foaming agents, iron, manganese and total dissolved solids. Treatment is reverse osmosis.

Conductivity is a measure of the conductance of an electric current in water. This is an easy measurement to make and relates closely to the total dissolved solids (mineral) content of water. The maximum contaminant level (MCL) is 0.4 to 0.85 micro-Siemens per centimeter. Treatment with reverse osmosis is effective for drinking water purposes.

Fluoride concentrations of 0.7 to 1.2 mg/l in drinking water will protect against dental cavities. However, excessive levels (more than 1.5 mg/l) may cause discoloration, or mottling of the teeth. This occurs only in developing teeth before they push through. Elevated fluoride levels also may cause skeletal damage and bone disease. Because low levels of fluoride are common in groundwater, most municipalities add fluoride to the water.

Iron in concentrations greater than 0.3 mg/l and manganese in concentrations greater than 0.05 mg/l may cause brown and black stains on laundry, plumbing fixtures and sinks. A metallic taste also may be present, and it may affect the taste of beverages made from the water. High concentrations of iron and manganese do not appear to present a health hazard. Treatment includes a water softener or iron filter for iron and reverse osmosis for manganese.

Refer to the list of publications later in this article for more information on softening, and iron and manganese removal.

The results reported for nitrates can be confusing because they may be reported as nitrogen (N) or nitrate-nitrogen or as nitrate (NO3). The following are the maximum levels for each:

• Nitrogen (N) or nitrate-nitrogen (NO3-N) should not be higher than 10mg/L.
• Nitrate (NO3) should not be higher than 45mg/L.

High nitrate levels may cause methemoglobanemia (infant cyanosis or “blue baby disease”) in infants who drink water or formula made from water containing nitrate levels higher than recommended.

Adults can drink water with considerably higher concentrations than infants without adverse effects. Treatment of such water includes anionic ion exchange, reverse osmosis, distillation and/or deionization

Refer to the list of publications later in this article for more information on softening.

The pH of water is a measure of acidity or alkalinity. The pH is a logarithmic scale based on a measure of the free hydrogen ions in the water. The scale runs from 0 to 14, where 7 is considered neutral, 0 to 7 is acidic and 7 to 14 is alkaline. Because pH can be affected by dissolved minerals and chemicals, it is an important indicator of the change in water chemistry.

According to the U.S. Environmental Protection Agency, drinking water with a pH between 6.0 and 9.5 generally is considered satisfactory. Several public water supplies that use the Missouri, James or Red River as their source of water have to maintain the pH above 9 keep them in compliance with the Lead and Copper rule of the Safe Drinking Water Act, which details how to prevent leaching of these elements from piping systems

Water with a pH below 6 or above 9.5 can be corrosive to metal plumbing pipes and fixtures. The pH of water can affect the performance of pesticides, particularly herbicides.

Potassium concentrations in water are generally very small. Although excessive amounts may have a laxative effect, the EPA has not established a maximum limit. Potassium (chloride) is used as a replacement for salt in water softeners when dietary sodium intake is a health issue.

Sodium is a very active metal that does not occur naturally in a free state. It always is combined with other substances. In the human body, sodium helps maintain the water balance. Human intake of sodium is mainly influenced by the consumption of sodium as sodium chloride or table salt. The contribution of drinking water is normally small, compared with other sources.

The treatment for certain heart conditions, circulatory or kidney diseases, or cirrhosis of the liver may include sodium restriction. Diets for these people should be designed with the sodium content of their drinking water taken into account.

The National Academy of Sciences has suggested a standard for public water allowing no more than 100 mg/l of sodium. This would ensure that the water supply adds no more than 10 percent of the average person’s total sodium intake.

The American Health Association recommends a more conservative standard of 20 mg/l to protect heart and kidney patients.

Softening by ion exchange or lime-soda ash increases the sodium content approximately 8 mg/l for each gr/gal (grain per gallon) of hardness removed. Treatment includes the use of potassium chloride instead of sodium chloride softener pellets (softener salt) or, alternatively, restricting drinking water from this source.

Water containing high levels of sulfates, particularly magnesium sulfate (Epson salts) and sodium sulfates (Glauber’s salt) may have a laxative effect on people unaccustomed to the water. These effects vary among individuals and appear to last only until they become accustomed to using the water. High sulfate content also affects the taste of water and forms a hard scale in boilers and heat exchangers. The upper limit recommended for sulfates is 250 mg/l. Treatment includes reverse osmosis.

High concentrations of TDS may affect taste adversely and deteriorate plumbing and appliances. The EPA recommends that water containing more than 500 mg/l of dissolved solids not be used if other less mineralized supplies are available. However, water containing more than 500 mg/l of TDS is not dangerous to drink.

Exclusive of most treated public water supplies, the Missouri River, a few freshwater lakes and scattered wells, very few water supplies in North Dakota contain less than the recommended 500mg/L concentration of total dissolved solids. Many households in the state use drinking water supplies with concentrations up to 2,000 mg/l and greater. Treatment for household use is reverse osmosis.

Hardness is the property that makes water form an insoluble curd with soap and primarily is due to the presence of calcium and magnesium. Very hard waters have no known adverse health effects and may be more palatable than soft waters. Hard water is primarily of concern because it requires more soap for effective cleaning; forms scum and curd; causes yellowing of fabrics; toughens vegetables cooked in the water; and forms scale in boilers, water heaters, pipes and cooking utensils.

The hardness of high-quality water should not exceed 270 mg/l (15.5 grains per gallon) measured as calcium carbonate. Water softer than 30 to 50 mg/l may be corrosive to piping, depending on pH, alkalinity and dissolved oxygen. Water softeners will correct hard water of more than 270 mg/l.

Refer to the list of publications later in this article for more information on softening.

Turbidity is a measure of suspended minerals, bacteria, plankton, and dissolved organic and inorganic substances. Turbidity often is associated with surface water sources. Treatment includes mixing with a substance such as alum that causes coagulation of the suspended materials, which then can be removed by sand filter filtration.