Clemson University Cooperative Extension Service
What
is the source of well water?
Well
water comes from ground water. Ground water is water from
rain and snow that filters through the soil into underground
storage areas called aquifers or into small openings between
rocks.
What
are the different types of wells?
The five
main types of wells are dug, drive, bored, drilled, and jetted
(washed down).
Most
dug wells were either built before drilling equipment
was available or because drilling was considered too expensive.
Modern dug wells are typically lined with concrete tile
and have a large diameter which provides a big opening to
the aquifer. This allows them to obtain water from materials
such as very fine sand, silt, or clay. Dug wells are shallow
and lack a continuous casing, making them subject to contamination
by nearby sources.
Driven wells are made by driving a small-diameter pipe
into shallow, water-bearing sand or gravel. These wells
are relatively simple and economical to construct, but they
can only tap shallow water and, like dug wells, are easily
contaminated.
Bored wells are constructed with a large auger. The
depth of bored wells is usually about 50 to 70 feet, and
they are usually built in soft materials such as sand, silt,
clay, and soft rock.
Either
percussion or rotary-drilling machines are used to construct
drilled wells. These wells can be more than 1,000
feet deep. Wells that penetrate land that is not hard and
solid require a casing and a screen to prevent the inflow
of sediment, which could cause the well to collapse.
High-pressure
water is forced into the ground to drill jetted or washed
down wells. This method of construction can only be
used in soft ground.
How
can I ensure that I will get an adequate water supply from
my well?
To provide an adequate household supply of water, a well should
be able to supply about 5 gallons of water per minute. The
availability of water in the surrounding soil or rock determines
the water supply rate. Where shallow ground water is plentiful
and of good quality, a shallow well may be adequate. To prevent
contamination, state regulations require that the space around
the casing be sealed in all wells.
Is
well water pure?
Ground
water is never completely pure. Minerals, chemicals, or microorganisms
such as bacteria and viruses can easily move with the water
as it moves down through the soil. Gasoline, diesel fuel,
or other chemicals from leaking underground storage tanks
may seep through the soil and into ground water. The type
and amount of these materials may vary, depending on the type
of soil and rock and the distance these materials travel.
What
are the sources of ground water contaminants?
Examples
of sources of ground water contamination which may threaten
human and animal health as well as the environment include:
Human
and animal wastes from septic tanks, lagoons, and other waste
storage facilities.
Any chemicals or cleaners that are poured down household sinks.
Landfills.
Leaking underground storage tanks.
Fuel pipelines.
Saltwater encroachment in coastal areas.
Improper use of fertilizers and pesticides.
Injection wells for disposal of wastes and drainage water.
(These wells are illegal in SC.)
Chemical spills.
How do
I know if my well water is contaminated?
Contaminated
water may look, taste, and smell fine. The only way to determine
if your well water contains harmful nitrate, bacteria, viruses,
or chemicals is to have it tested. Generally, water testing
is done only if there is sufficient reason to suspect that
contamination is present. The following symptoms or conditions
could also indicate natural problems.
A"rotten
egg" odor may be caused by HYDROGEN SULFIDE.
Problems
with soap sudsing or cleaning, or scum build-up on shower
curtains or fixtures may indicate HARDNESS.
Red
water and staining of laundry or plumbing fixtures may indicate
the presence of IRON or MANGANESE.
If
pipes are corroding or blue copper stains are appearing
on plumbing fixtures, the water should be checked for pH
and CORROSIVENESS.
Any
sudden changes in taste, color, or odor may indicate a problem.
The presence
of other contaminants (some of which could cause severe health
problems) do not have any visible effects. If you suspect that
there might be a problem with the quality of your water supply,
have the water tested.
How
do detergents, fertilizers, pesticides, and fuels affect well
water quality?
The
use of detergents, fertilizers, pesticides, or fuels does
not automatically cause contamination. Misuse is the problem.
Ground water contamination from domestic land use is most
commonly associated with septic disposal systems or improper
storage, use, or disposal of household and lawn chemicals.
It is important to carefully follow the directions on labels,
heed all warnings, and properly dispose of hazardous substances.
Does
agriculture or industry pose a threat to water quality in
South Carolina?
The
use of farm fertilizers, pesticides, and animal-waste lagoons
has caused some contamination of shallow aquifers, but when
agricultural chemicals are used and stored properly, it is
rare for them to reach ground water supplies in amounts that
cause problems. In many cases of contamination involving wells
located near agricultural land, contamination can be traced
to spills that occurred during the preparation, mixing, or
handling of chemicals before application or from infiltration
of rinse water used to clean application equipment or tanks.
All chemicals should be stored safely and far from water sources.
Industrial areas also contribute pollutants. The most common
industrial sources of ground water contamination are landfills,
waste lagoons, and leaking underground storage tanks. As we
have seen with domestic and agricultural practices, with care
and proper handling of potentially harmful materials the risk
of contamination can be greatly decreased.
How
do I get my well water tested? How expensive is it?
Contact your county health department or your county office
of the South Carolina Cooperative Extension Service to find
out which labs do water testing.
Normally,
the cost of testing ranges from $15 to $250, depending on
what the water is being tested for. Detecting specific viruses
or individual chemicals is very time consuming and expensive.
Before having your water tested, ask local experts such as
Extension specialists, water treatment plant officials, or
state and local health and environmental agencies for advice
about which tests should be done on your water. When testing,
make sure you follow the sampling techniques given by the
lab.
What
can homeowners do to improve the quality of well water?
In a
bacteria-contaminated water system, chlorination of the well
is commonly recommended as a solution. Another option is filtering
or treating the water at the tap. Otherwise, to fully correct
the water supply, the source of contamination must be removed
or the water must come from a new well that is not affected
by the contaminated source or that taps a deeper aquifer.
Can
a well go dry?
How
does it happen?
Wells
do stop supplying water, either because they go dry or due
to other factors. In some instances, what happens is that
the water table drops below the pump intake level or the intake
screen at the end of the pump becomes clogged. Once the problem
is corrected or the ground water level rises, the wells are
back in action.
Several
situations can lower the water level to the point of "dry"
wells. Drought or seasonal declines in the water level most
commonly affect shallow wells. Increased pumping will also
lower the water level. High rates of pumping for industrial,
municipal, or agricultural purposes can drop the water table
below existing wells.
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
This
publication was supported in part by the US. Department of
Agriculture, Extension Service, Well Head Protection under
special project number 3-36-XXXX-0357-13-4425
The
Clemson University Cooperative Extension Service offers its
programs to people of all ages, regardless of race, color,
sex, religion, national origin, or disability and is an equal
opportunity employer. Clemson University Cooperating with
U.S. Department of Agriculture, South Carolina Counties. Issued
in Furtherance of Cooperative Extension Work in Agriculture
and Home Economics, Acts of May 8 and June 30, 1914
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