Interpreting Your Water Test Reports
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The following information was taken from an NDSU
Extension Service Report, Interpreting Your Water Test Report, November 1987.
Alkalinity:
Alkalinity is a measure of the capacity of water to neutralize acids. The predominant
chemical system present in natural waters is one where carbonates, bicarbonates and
hydroxides are present. The bicarbonate ion is usually prevalent. However, the ratio of
these ions is a function of pH, mineral composition, temperature and ionic strength. A
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 is generally associated with high
values, and
excess . High alkalinity waters may also
have a distinctly flat, unpleasant taste.
Calcium and Magnesium:
Calcium and Magnesium are important contributors to water hardness. When water is heated
they break down and precipitate out of solution, forming scale. Maximum limits have not
been established for these parameters. Magnesium concentrations greater than 125 mg/L may
have a laxative effect on some people.
Chloride:
High concentrations of chloride ions may result in an objectionable salty taste to water
and the corrosion of plumbing in the hot water system. High chloride waters may also
produce a laxative effect. An upper limit of 250 mg/L has been set for the chloride ions,
although at this limit few people will notice the taste. Higher concentrations do not
appear to cause adverse health effects. An increase in the normal chloride content of your
water may indicate possible pollution from human sewage, animal manure or industrial
wastes.
Conductivity:
Conductivity is the measure of the conductance of the water to an electric current.
Conductivity is commonly reported as umhos/cm (micromhos per centimeter). This is an easy
measurement to make and relates closely to the total dissolved solids content of the
water. The total dissolved solids is approximately 70 percent of the conductivity in
umhos/cm.
Fluoride:
At concentrations greater than 1.0 mg/L, fluoride will reduce the incidence of dental
cavities. At concentrations greater than 1.5 mg/L, fluorosis (mottling) of teeth may
occur. Most municipal water supplies have added fluoride to reach the optimal level of 1.2
mg/L to reduce cavities. Some water supplies in North Dakota contain naturally occurring
fluoride in amounts high enough to cause mottling of the teeth.
Iron and Manganese:
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 may also 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.
Nitrate:
Nitrate levels should not be higher than 10 mg/L if reported as nitrogen (N). High nitrate
may cause methemoglobinemia (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 affects. Livestock water can contain up to 100 mg/L of nitrate as
nitrogen, but young monogastric animals such as hogs may be affected at nitrate levels
considerably less than 100 mg/L.
pH: pH is a
measure of the hydrogen ion concentration of the water. The pH of water indicates whether
the water is acid or alkaline. The measurement of pH ranges from 1 to 14 with a pH of 7
indicating a neutral solution, neither acid nor alkaline. Numbers lower than 7 indicate
acidity; numbers higher than 7 indicate alkalinity. Drinking water with a pH of between
6.5 and 8.5 is generally considered satisfactory. Acid waters tend to be corrosive to
plumbing and faucets, particularly if the pH is below 6. Alkaline waters are less
corrosive. Waters with a pH of above 8.5 may tend to have a bitter or soda like taste. The
pH of water may have an effect on the treatment of water and also should be considered if
the water is used for field application of pesticides. Water with a pH of 7.0 to 8.5 will
require more chlorine for the destruction of pathogens than will water that is slightly
acidic.
Potassium:
Potassium concentrations in water are generally very small. Although excessive intakes may
have a laxative effect, public health authorities have not established a maximum limit.
Sodium:
Sodium is a very active metal which does not occur in nature in a free state. It is always
combined with other substances. In the human body sodium helps maintain 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 to
other sources. The treatment for certain heart conditions, circulatory or kidney diseases
or cirrhosis of the liver may include sodium restriction. Diets for these persons 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 insure that the water supply adds no more than 10
percent of the average person's total sodium intake. The American Health Association has
recommended a more conservative standard of 20 mg/L to protect heart and kidney patients.
High concentrations of sodium will reduce the
suitability of water for or house plant
watering use. High sodium water will alter the soil chemistry and absorption properties,
eventually sealing the soil surface.
Softening water by ion exchange or lime-soda ash
processes will increase the sodium content. Softening by ion exchange will increase the
sodium content by approximately 8 mg/L for each grain per gallon of hardness removed.
Sulfate:
Water containing high levels of sulfates, particularly magnesium sulfate (Epsom salts) and
sodium sulfate (Glauber's salt) may have a laxative effect on persons unaccustomed to the
water. These effects vary with the person and appear to last only until one becomes
accustomed to using the water. High sulfate content also affects the taste of water and
will form a hard scale in boilers and heat exchangers. For these reasons the upper
recommended limit for sulfates is 250 mg/L.
Total Dissolved Solids:
High concentrations of total dissolved solids (TDS) may cause adverse taste effects.
Highly mineralized water may also deteriorate domestic plumbing and appliances. It is
recommended that waters containing more than 500 mg/L of dissolved solids not be used if
other less mineralized supplies are available. This does not mean water containing more
than 500 mg/L TDS is unusable. Exclusive of most treated public water supplies, the
Missouri River, a few fresh lakes and scattered wells, very few water supplies in North
Dakota contain less than 500 mg/L concentration of total dissolved solids. Many households
in the state use drinking water supplies with concentrations of 2000 mg/L and greater.
Total Hardness:
Hardness is the property which makes water form an insoluble curd with soap and is
primarily due to the presence of .
Waters which are very hard 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 good quality water should not
exceed 270 mg/L (15.5 grains per gallon) measured as calcium carbonate. Water softer than
30-50 mg/L may be corrosive to piping depending on ,
and dissolved oxygen.
Turbidity:
Turbidity is a measure of light transmission and indicates the presence of suspended
material such as clay, silt, finely divided organic material, plankton and other inorganic
material. Turbidities in excess of 5 are usually objectionable for aesthetic reasons. If
turbidity is high, be aware of possible bacterial contamination.
Irrigation Water Quality
The following image was taken from the
California State Water Resources Control Board, Water Quality Criteria Manual
Retrieve the same image at a , making it
easier to read.
Irrigation water must be considered from the
standpoint of the total salts (salinity) it contains and the amount of sodium (alkalinity)
it carries. Both factors will prove harmful if they are allowed to accumulate in the soil.
The sodium is usually the more serious problem.
In North Dakota many groundwater sources are
unacceptable for irrigation. The suitability of water for irrigation depends both upon the
water itself and upon the soil it is to be used on. A sandy soil can take a poorer quality
water than a clay soil because the water carries away the salts and sodium as it drains.
The County Extension Agent has a knowledge of
the soil conditions in your area, and should be consulted for more specific information
concerning irrigation waters.
The salinity hazard of
irrigation water is measured as electrical
in terms of micromhos/cm at 25 degrees C.
C-1 (0-250 micromhos): Low
salinity water can be used for irrigation with little likelihood that soil salinity will
develop.
C-2 (250-750 micromhos): Medium
salinity water can be used for irrigation if a moderate amount of leaching occurs.
C-3 (750-2250 micromhos): High
salinity water should be used only on soils of moderate to good permeability. Leaching is
needed to prevent serious soil salinity.
C-4 (above 2250 micromhos):
Very high salinity water is generally undesirable for irrigation and should be used only
occasionally on soils of good or high permeability where special leaching is provided to
remove excess salt.
The
hazard of irrigation water is dependent on the Sodium Adsorption Ratio (SAR) and the
electrical conductivity of the water.
S-1: Low sodium water can be
used on almost all soils with little danger of accumulating harmful amounts of
exchangeable sodium.
S-2: Medium sodium water can be
used on coarse textured soils with good permeability but is dangerous when used on fine
textured soils.
S-3: High sodium water tends to
cause harmful sodium accumulations and requires special soil management, good drainage,
high leaching, and organic matter additions.
S-4: Very high sodium water is
generally unsatisfactory for irrigation purposes.
