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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 especially important if you have a well because it could impact your drinking water quality or water source if not maintained.

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 Onsite Wastewater Bureau (link below in Downloads and Resources).

Water Treatment Basics

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.

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 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.

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.

Spongy areas in the drain field can indicate septic system failure.

Some signs a septic system is failing

  • 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.

Tips for septic systems

  • The sludge and scum should be periodically pumped out of the tank.
  • Conserve water to avoid overloading the 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.
  • Do not dump hazardous chemicals in your drain, they can destroy biologic digestion and ruin the system.

Septic Systems, Water Quality, and Health

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.

Preventing groundwater contamination from septic systems

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 indicate if contamination has occurred. If contaminated, nearby septic systems may be the culprit. Other preventive measures include:

  • 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 (3)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 system regulations are intended to minimize the chance for groundwater to be contaminated by human waste.

What you can do after contamination

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). For microbial contamination: disinfection following safe guidelines (pdf in Downloads and Resources).

Boil 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.

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

How contamination can affect your health

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.

Proper siting of a septic system is important if you have a well for drinking water.

Septic Systems and Flooding or Other Disasters

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 or sewage is visible outside.

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 and 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.
  • 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.