I get asked a lot of questions about well water in the office. That’s not surprising since 15-20% of US households get their water from private wells. Unlike municipal water supplies,
private wells are not bound by federal regulations. And aside from initial
inspections during drilling, state regulation of private wells is minimal. It
is up to the owners of the wells to have their water tested and it is up to us
as pediatricians to make specific recommendations. Let me give you an idea of
Groundwater collects under the topsoil and above the bedrock forming what
is called an aquifer. The water table, or the depth at which the aquifer is
saturated with water, varies according to the seasons. Aquifers are replenished
with rain water and run-off and the water is filtered naturally on its journey
underground. Wells take advantage of this naturally-occurring water in the
earth by different methods. Old-fashioned dug wells were nothing more than
shallow, lined holes with a pump at the spigot. They were easily contaminated.
Drilled wells, on the other hand, reach the bedrock some 100 to 400 feet below
the earth’s surface. They have an electric pump at the bottom of the well. In
positioning wells, home-owners should strive to keep them as far as possible
from septic fields and from areas which house livestock or store fertilizers or
Well water can be contaminated by both micro-organisms and by organic
and inorganic chemicals. These contaminants vary regionally (for example,
contamination from crop fertilizers in the mid-west vs. sea salt contamination
in coastal communities. Arsenic is a fairly common contaminant of well water. A
recent study from the US Geological Survey found that 13% of some 2000 wells tested in New England exceeded federal safety standards for public drinking water. While no arsenic poisonings from well
water have been reported from well water in this country, arsenic is a known
cause of bladder, skin and lung cancer.
Uranium contamination occurs mostly in the mountainous western US
although areas with much granite are also at risk. Radon, another naturally
occurring radioactive gas similar to uranium can also contaminate well water.
Radon can be consumed directly by drinking, but exposure can also occur
showering and cleaning with contaminated water. Perchlorate is a
naturally-occurring chemical used in rocket fuel and fireworks that can also
contaminate well water. Importantly, perchlorate can interfere with thyroid function.
Nitrates are one of the most common contaminants of well water. They can
come from either sewage or fertilizers. If well water testing detects nitrates,
further testing for coliform bacteria should be done. If no coliforms are
detected, the source of the contamination is likely fertilizer. Nitrates with
coliforms suggests contamination from either livestock or human sewage. Water
with > 10mg/L of nitrate should not be given to children younger than age
Speaking of micro-organisms, not only bacteria but also parasites,
funguses and even viruses can contaminate well water. Testing for these
organisms can be confusing because not all organisms found necessarily cause
disease. Also, the absence of coliforms on a well water test does not necessarily
mean that fecal contamination is not present. Families can learn where to have
their well water tested by contacting their local Department of Public Health
or US Environmental Protection Agency. Testing can be expensive and the American Academy of Pediatrics encourages
states and municipalities to provide free or low-cost testing to families who
cannot afford it.
If contaminants are found in a family’s well water, there is plenty that
can be done to eliminate the contaminants or lessen their toxic effects. If
bacteria are found, the well should first be inspected to look for damage or
defects and any structural problems repaired. In consultation with local health
departments, water can be treated with high concentrations of chlorine then
flushed out of the system and re-tested. Carafe-style and faucet-mounted
filters can reduce lead, sediment, some organic materials as well as Giardia and Cryptosporidium cysts.
But they are designed for use with municipal
water and should not be counted on to filter contaminated well water.
Ultraviolet light, ozone or hydrogen peroxide can remove or kill many
micro-organisms. Reverse-osmosis filtration systems can remove many kinds of
contamination but are expensive.
Regardless of the kind of contamination—chemical or bacterial—the source
of the contaminant should be located and corrected. Homeowners can seek help in
testing and treating their water by contacting NSF International, a non-profit,
non-governmental agency that tests and certifies consumer products.
Well water can be safely consumed by families, but vigilance, regular
testing and, if needed, treating is necessary.
1. “Drinking Water from Private
Wells and Risks to Children.” Pediatrics. Vol 123, No. 6 June 2009.
“Troubling Findings in Some N.E. Wells.” Boston Globe. June 28, 2012.