Guidance for Private Well Owners
Private Well Owners
If you rely on a private well for your drinking water, it’s your responsibility to have your water tested. The
Safe Water Drinking Water Act only applies to public water systems (defined as serving at least 25 people
or 15 service connections for at least 60 days per year) and does not apply to you. The Drinking Water
Bureau does not collect water samples or pay for the analysis of samples from private wells.
How to do Water Testing
Homeowners are responsible for private wells. To help protect your well, here are some steps you can
1. Have your water tested annually by a private laboratory. (You will have to pay for this service).
2. Bring in a water sample to a New Mexico Environment Department (NMED) water fair. (This
service is free).
NMED offers Free Water Testing
Where can I get my drinking water tested?
1. Water Fairs. If you are using private well water, the NMED will test your water for free during Water
Fairs scheduled around the state. The water fair and water-quality outreach program consists of
approximately 10 water fair events per State Fiscal Year (July 1 to June 30), conducted in rural
communities throughout New Mexico. To the extent possible, the events will be evenly distributed
among five NMED Districts. Each water fair event will include the following:
Water samples from private domestic wells will be tested using portable analytical equipment. The
free testing includes:
If you would like to request a water fair in your community please contact Melanie Sanchez at (505)
2. Field Offices and the Runnels Building. Currently NMED offers free well testing at each of the 22
Field Offices and at the Runnels Building in Santa Fe. This service may be discontinued sometime in
2012. For more information see the free well testing webpage:
3. Private Laboratory. Additionally, you can hire a private laboratory to do the test. Look under
“laboratories-testing” in the Yellow Pages or see a list of state certified labs
What Tests are needed?
If you have recently drilled a new well or moved to a home where the existing well is new to you, it’s
important to test the water as soon as possible so you can begin monitoring the water quality.
NMED recommends that you test your water every year for total coliform bacteria and nitrites/nitrates.
Common acute health risks associated with bacteria and nitrate can negatively impact your health in the
immediate future. For example, infants under the age of 6 months old who are exposed to high levels of
nitrate could develop blue baby syndrome and become seriously ill or die.
Several naturally occurring chronic contaminants exist in New Mexico groundwater. The most common
chronic contaminants include Arsenic, Uranium, and Fluoride. NMED recommends that these
contaminants be tested every three years.
Arsenic levels in excess of .010 mg/l have been linked to cancer of the bladder, lungs, skin, kidney, nasal
passages, liver, and prostate. Non-cancer effects can include thickening and discoloration of the skin,
stomach pain, nausea, vomiting; diarrhea; numbness in hands and feet; partial paralysis; and blindness.
Uranium levels in excess of .030 mg/l can result in increased cancer risk, liver damage, or both, or
increased risk of kidney damage. Long term chronic intakes of uranium isotopes in food, water, or air can
lead to internal irradiation and/or chemical toxicity. The individual risk depends on the concentration,
amount consumed, for how long as well as the age and general health of the individual.
The current enforceable drinking water standard for fluoride is 4.0 mg/L. This is the maximum amount that
is allowed in water from public water systems, also called the Maximum Contaminant Level. Adults
exposed to excessive consumption of fluoride over a lifetime may have increased likelihood of bone
fractures, and may result in effects on bone leading to pain and tenderness. Teeth may also be affected.
Children are most likely to be affected by excessive exposure to fluoride because it impacts teeth while
they are still in formative phases. Children aged 8 years and younger exposed to excessive amounts of
fluoride have an increased chance of developing pits in the tooth enamel, along with a range of cosmetic
effects to teeth. A secondary standard is a non-enforceable guideline to regulate contaminants that may
cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or
color of drinking water). EPA recommends secondary standards to water systems but does not require
systems to comply. For fluoride, the secondary standard is 2.0 mg/L.
When you are considering what to test for, consider which factors could be impacting the source of your
drinking water. Check drinking water watch for local community well data which will provide information
about natural contaminants that may be present in your region https://eidea.nmenv.state.nm.us/SDWIS/.
Chemical tests can be expensive, so you may want to limit them to possible problems specific to your
situation. Contact the Drinking Water Bureau if you have any questions. The table below lists some
potential problems and the appropriate tests to identify contaminant sources.
Common Sources of Potential Ground Water Contamination
Category Contaminant Source Consider Testing for
Agricultural Animal burial areas Nitrate, pesticides (also called
Drainage fields/wells synthetic organic compounds),
Animal feedlots coliform bacteria
Manure spreading areas/pits,
Commercial Airports Volatile organic compounds, total
Jewelry/metal plating dissolved solids, pH, sulfate,
Auto repair shops chloride, metals
Cemeteries Process waste water
Dry cleaners fields/wells
Railroad tracks and yards
Scrap and junkyards
Industrial Asphalt plants Metals, pH, corrosion, Volatile
Petroleum production/storage organic compounds, total
Chemical manufacture/storage dissolved solids, sulfate
Process waste water drainage
Septage lagoons and sludge
Mining and mine drainage
Toxic and hazardous spills
Wood preserving facilities
Residential Fuel Oil Volatile organic compounds, total
Septic systems, cesspools dissolved solids, pH, sulfate,
Furniture stripping/refinishing chloride, metals, coliform
Municipal Sewer lines bacteria, and nitrates
Household hazardous products
Swimming pools (chemicals)
Other Hazardous waste landfills Volatile organic compounds, total
Recycling/reduction facilities dissolved solids, pH, sulfate,
Municipal incinerators chloride, metals
Road deicing operations
Road maintenance depots
Storm water drains/basins/wells
Open burning sites
Testing more than once a year may be warranted in special situations:
someone in your household is pregnant or nursing
there is an infant in the household
there are unexplained illnesses in the family
your neighbors find a dangerous contaminant in their water
you note a change in water taste, odor, color or clarity
there is a spill of chemicals or fuels into or near your well
when you replace or repair any part of your well system, pipes or hot water heater.
Protect the Well
Ensuring a clean safe drinking water supply by reducing the threat of waterborne illnesses helps save
costs by eliminating health care expenses and additional treatment costs. Examples of some methods
of protecting source water are listed below.
Activity or Threat Impact Best Management Practice
Septic Systems Possible fecal or Nitrite/Nitrate Proper location of the septic
contamination of the well water. system, a minimum of 200 feet
from the well. Properly maintain
the septic system.
Lawn and Garden Fertilizer Nitrogen leaching into drinking Select appropriate fertilizer and
water supplies. avoid applying near wells.
Pet Waste Direct contact can introduce Ensure well head has a proper
wastes to drinking water sanitary seal (surface runoff
supplies. cannot enter well casing or run
down side of casing). Pick up
Sewer Overflows Discharge of untreated sewage Prevention methods such as
through broken pipes, equipment visual inspections, monitoring
failures and overloads. and maintenance. Proper septic
Storm Water Runoff Rain or snow runoff carrying Ensure well head has a proper
sediments and contaminants into sanitary seal (surface runoff
groundwater. cannot enter well casing or run
down side of casing).
Shock chlorination table for the wells
Shock chlorination is a method of disinfecting a water well. It is the recommended treatment when a water
system is contaminated with bacteria. Contamination can occur when the well is installed, when repairs
are made to the pump or plumbing, or when rainfall runoff enters the well. The shock chlorination table
below identifies the amount of chlorine bleach needed for shock chlorination.
Amount of chlorine bleach needed for shock chlorination
Laundry Bleach (about 5.25% hypochlorite)
Standing water Casing Diameter
depth in well 4 inches 6 inches 8 inches 10 inches 12 inches
10 ½ cup 1 cup 1 ½ cups 1 pint 2 pints
25 1 cup 1 pint 2 pints 3 pints 4 ½ pints
50 1 pint 1 quart 2 quarts 3 quarts 1 gallon
100 1 quart 2 quarts 1 gallon 1 ½ gallons 2 gallons
150 3 pints 3 quarts 1 ½ gallons 2 gallons 3 gallons
After shock chlorination treatment, the well owner should use a chlorine residual test to determine if the
chlorine has killed the bacteria and if the water is safe to drink again. The Chlorine residual tests will
indicate if a sufficient amount of chlorine was added initially to the water to inactivate the bacteria and
some viruses that cause diarrheal disease. For more information on how to conduct a chlorine residual
test and interpret the results please see:
Both private and public wells require constant pressure for the convenience of the end user. A private well
requires a water pump and a separate pressurized tank system. These two components work together
along with an electric pressure switch to ensure that a steady and consistent water flow from indoor
faucets can be delivered. If the well or water pump begin to cycle (turn on and off) more than six times in
an hour there may be an issue with the pressure tank. Common pressure tank issues include incorrect
pressure settings or inappropriate air pressure. Contact a licensed plumber for more information.