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water. Coliforms are useful indicators of the possible presence of pathogenic
bacteria and viruses.
Conductivity (E.C.) – is measured in decisiemens/meter (dS/m). It can
be used to estimate the total dissolved solids in the water. Multiplying the
conductivity in dS/m by 640 will give a good approximation of the total dis-
solved solids in mg/L. Conductivity tests are often used to assess water suit-
ability for irrigation. Conductivity is sometimes expressed as microSie-
mens/cm (µS/cm OR uS/cm), which is 1000 times smaller as a unit than deci
siemens per centimeter. (Eg 0.75 decisiemens/m=750 microsie-
mens/cm=0.750 millisiemens/cm). We have used the letter "u" within our
tool to represent the "micro" prefix "µ". We have used the conversion of
1dS/m = 700 mg/L TDS within the tool because the federal guidelines have
used this conversion for their guidelines values for TDS.
Fluoride – occurs naturally in most groundwater wells and can help
prevent dental cavities. Between 1 and 1.5 mg/L is desirable. As fluoride lev-
els increase above this amount, there is an increase in the tendency to cause
tooth mottling. Fluoride levels less than 2 mg/L are not considered a problem
for livestock.
Hardness – caused excessive soap consumption and scaling. Hardness
is caused primarily by calcium and magnesium, but is expressed as a mg/L
equivalent of calcium carbonate. Hard water causes soap curd, which makes
bathroom fixtures difficult to keep clean and causes greying of laundry. Hard
water will also tend to form scale in hot water tanks, kettles, piping systems,
etc.
Iron – levels as low as 0.2 to 0.3 mg/L will usually cause the staining of
laundry and plumbing fixtures. The presence of iron bacteria in water sup-
plies will often cause these symptoms at even lower levels. Iron gives water a
metallic taste that may be objectionable to some at 1 to 2 mg/L. Most water
contains less than 5 mg/L iron, but occasionally, levels over 30 mg/L are
found.
Maximum Acceptable Concentration (MAC) - levels of substances
that are known, or suspected to, cause adverse effects on health.
NO3 nitrogen (Nitrate) – is often an indicator of contamination by hu-
man or livestock wastes, excessive fertilization or seepage from dump sites.
The maximum acceptable concentration in drinking water is 10 mg/L. This
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