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Septic Systems and Private Wells

If you have a private well, it is likely you also have a septic system. An estimated 20 percent of houses in the United States are served by septic systems. Maintaining your septic system is associated with your well because it could impact your drinking water quality or water source if not well managed.

There are regulations for home liquid waste systems aimed at protecting drinking water quality. You can learn about those and get tips about maintenance and permits from the New Mexico Environment Department's Liquid Waste Program.
A septic system is made up of a pipe leading from the home into a septic tank. Septic tanks typically have one or two chambers. From the tank piping leads into the drain-field and the surrounding soil.

A typical septic system contains a septic tank and a drain-field, also called a leach field or absorption field.
  • Water is discharged out of the house into a main drainage pipe into a septic tank.
  • The septic tank is a buried, water-tight container. Tanks are usually made from concrete, fiberglass, or polyethylene. Inside the tank, the wastewater settles and separates: solids settle to the bottom forming sludge, liquid water is in the middle, and oil and grease floats to the top as scum. The tank is designed to prevent the sludge and scum from leaving the tank and entering the drain-field area.
  • The sludge and scum should be periodically pumped out of the tank.
  • The wastewater (effluent) flows out of the tank into the drain-field.
  • The drain-field contains a series of shallow, perforated pipes allowing the water to disperse into unsaturated soil. Wastewater is discharged into porous surfaces where it filters though the soil.
  • The wastewater percolates through the surrounding material (soil, gravel, or sand). This process removes excess nutrients and harmful microorganisms including: bacteria (coliform bacteria) and viruses. Coliform bacteria can live in the intestines of humans or other warm-blooded animals and can indicate human fecal contamination. Learn more about microorganisms and groundwater.
  • Ultimately the naturally treated wastewater is discharged to groundwater. The drain-field can be saturated with too much liquid. If this happens, the field may flood, and sewage backups may occur. If problems occur or you suspect a system malfunction, consult a septic professional (see septic system resources).
A sewage odor can be a sign something is wrong but is not always the first indicator of a problem with your septic system. Some things to look for include:
  • Drains backing up in the house.
  • The drain-field contains a bright green spongy area.
  • Water pooling around the septic tank or drain-field.
  • A strong sewage odor noticeable near the tank or drain-field.
Basic tips for septic system owners include:
  • Conserve water to avoid overloading system.
  • Do not treat it like a trash can, this will decrease the effectiveness of your septic system.
  • Avoid dumping grease down the drain, it solidifies and can clog your septic system and do not put any hazardous chemicals or substances in your septic system, they can destroy biologic digestion and ruin your septic systems.
Septic systems that are failing or improperly constructed may contribute to groundwater contamination. Many septic owners also rely on private water wells, which use groundwater, for their drinking water. Well owners with septic systems can take steps to protect their groundwater and their (families) health, including:
The best way to know if your water is safe to drink is to test it. Annual tests (spring is best) for fecal coliform bacteria and nitrate can help indicate if contamination has occurred. If contamination has occurred, nearby septic systems may be the culprit. Learn more about well water testing.

Proper construction and maintenance of the well and the septic system can help protect from groundwater contamination.
  • Make sure your well has a sanitary cap or seal.
  • Make sure the ground is sloped away from the well so water flows away from the well head.
  • Make sure the casing extends 18 inches above the land surface (NMAC 19.27.4).
  • Private wells should be at least 50 feet from septic tanks and at least 100 feet from drain-fields. Septic systems regulations are intended to minimize the chance for groundwater to be contaminated by human waste.
Learn more about septic system regulations from the New Mexico Environment Department.
Treat your water:
  • For additional guidance choosing a treatment system certified to remove microorganisms (or other contaminants of concern) consult with the Water Quality Association or at 630-505-0160 or NSF international (formerly the National Sanitation Foundation) or at 1-800-NSF-MARK (1-800-673-6275) Learn more about treatment.
  • For microbial contamination: disinfection following safe guidelines. Learn more about disinfecting drilled wells with chlorine bleach.
  • Boiling your water: if your water has tested positive for bacteria, boiling it to kill germs may be a good option. Water should be brought to a rolling boil for 1 minute. At altitudes greater than 6,562 feet, boil water for 3 minutes. If the water contains other potentially harmful chemicals or constituents, boiling the water may concentrate them. The best way to know what is in your water is to test it. Learn more about boil water guidelines.

Maintain your septic system:
  • Have your system inspected by a professional every 1-2 years and pumped when necessary. Checks should include:
    • The amount of solids in the tank.
    • The inspection port.
    • The effluent (outlet) filter.
    • An inspection of the drain-field for damp or soggy areas.

Some tools for finding a septic professional in your area:

National Onsite Wastewater Recycling Association

National Association of Wastewater Technicians

Contact the New Mexico Environment Department - Liquid Waste Program

Microorganisms including bacteria, parasites and viruses associated with human or animal waste can get into groundwater (well water) and cause illness. The most common type of illness experienced is gastrointestinal with symptoms such as: stomach cramps or pain, diarrhea (sometimes bloody), vomiting, and fever. Depending on the organism, symptoms can last from 5 days to 6 weeks. Learn more about water related diseases and private wells.
During heavy rains or flooding, the system might not operate properly due to saturated soil around the system. A tank may even float or collapse. The system might not be operating properly if:
  • Sinks and toilets are slow to drain.
  • Drains are overflowing.
  • Sewage is visible outside.
Steps can be taken before, during, and after an emergency (such as a flood, wildfire or earthquake) to help prevent injury or illness.

Before an emergency

To prepare your septic system before an emergency:
  • Seal the manhole and/or inspection ports to prevent excess water getting into the septic tank.
  • If your septic tank is at least half full, this will help to prevent it from collapsing or floating.
  • If your system uses electricity:
    • Turn off the pump at the circuit box.
    • Waterproof any electrical connections.

During an emergency

  • Reduce the amount of water going into the system by limiting toilet flushing, laundry, dishwashing, and showering.
  • Use water (for drinking and cooking) from a clean alternate source until you can be sure your well water has not been contaminated. Learn more about private wells and disasters.
  • Avoid standing water that may be contaminated with sewage.

After an emergency

  • Do not drink your well water until you know it is safe. The best way to know if your water is safe to drink is to test it. Use an alternate safe water supply (like bottled or treated water).
  • Reduce nonessential water use (such as: dishwashing, washing clothes, and showering).
  • Flush toilets as little as you can. Use a temporary toilet if needed.
  • Avoid contact with electrical devices until they are clean and dry.
  • If the area is saturated with water, the tank should not be pumped more than halfway to prevent floating.
  • Get your septic system (and well) professionally inspected and repaired (see septic system resources).

Learn more about septic systems and emergency preparedness and response from the Centers for Disease Control and Prevention.

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Content updated: Thu, 2 May 2019 13:55:47 MDT