Households and businesses not served by public sewers rely on an onsite wastewater disposal system, or septic system, to treat and dispose of wastewater. Proper design, installation, and maintenance are critical for the prevention of pollution and disease caused by human waste.
St. Clair County has approximately 30,000 homes with septic systems. If left unattended a failing system can become a major source of fecal coliforms in the soil, ground, and surface water. Management is the key to a lasting septic system.
Permit Instructions:
Prior to installing or repairing a septic system, a sewage permit must be obtained from the Health Department. Instructions and applications are available for both residential and commercial buildings that generate less than 10,000 gallons of sewage per day.
For questions regarding an existing or proposed septic system, contact the Environmental Health Division at (810) 987-5306 to speak with the Sanitarian assigned to the area.
How a Septic System Works:
A septic system has four main components: a pipe from the home or business, a septic tank, a drainfield, and the soil. Wastewater from the toilet, bath, kitchen, and laundry flows through a pipe into the septic tank. Microbes in the soil digest or remove most contaminants from the wastewater before it reaches groundwater.
The Septic Tank:
A septic tank intercepts, holds, and partially treats solids. The tank is a large, buried, watertight container typically made of concrete, fiberglass, or polyethylene. Wastewater stays long enough to allow heavy solids to settle to the bottom (forming sludge) and oil and grease to float to the surface (as scum). Solids that do not decompose remain in the tank. Without periodic pumping, solids accumulate until the drainfield overflows, causing costly repairs.
Tanks may have one or two compartments. Two-compartment tanks settle solids more effectively. Tees or baffles at the inlet and outlet pipes slow incoming waste and keep solids inside the tank. All tanks should have accessible covers for checking baffles and for pumping.
The Drainfield:
Wastewater exits the septic tank and enters the drainfield for further treatment by the soil. Generally, the drainfield has a network of perforated pipes laid in gravel-filled trenches or beds. Wastewater trickles out of the pipes, through the gravel, and into the soil. The size and type of drainfield depends on estimated daily wastewater flow and soil conditions.
The soil filters waste as it passes through pore spaces. Microorganisms in the soil provide final treatment by removing harmful bacteria, viruses, and nutrients. After passing into the soil, most sewage infiltrates downward and outward, eventually reaching groundwater.
Care and Maintenance:
On-site systems differ from municipal sewer; there is a limited life expectancy, which can be drastically reduced if the system is improperly used or neglected. A septic system should provide many years of trouble-free service if properly maintained. Maintenance is less costly than replacement.
When septic systems are adequately designed, carefully installed, and properly maintained, the systems effectively reduce or eliminate most human health and environmental threats posed by pollutants in wastewater. Routine maintenance is more cost efficient than emergency repairs and much less expensive than total system replacement.
- Financial Savings: Regular pumping (every 3–5 years) is a bargain compared to the cost of replacing an entire system. Failing septic systems are expensive to repair, and poor maintenance is often the culprit.
- Property Investment Protection: An unusable septic system or one in disrepair lowers property value and could pose a legal liability. For a home sale, the disposal system must be in good working order.
- Health Protection: Safe sewage disposal prevents the spread of infection and disease while protecting groundwater resources. Inadequately treated sewage can cause groundwater contamination, posing a significant threat to wells and drinking water.
How to Maintain a Septic System:
- Pump Frequently: Systems should be pumped every 3-years depending on the number of residents and the size of the system.
- Use Water Efficiently:Using more water than the soil can absorb is the most common reason for failure. Water conservation reduces the volume entering the septic system. Efficient water use improves operation and reduces the risk of failure.
- Replace existing toilets and shower heads with high-efficiency models.
- Install aerators in kitchen and bathroom faucets.
- Repair leaky faucets and toilets.
- Run the dishwasher and clothes washer only when full.
- Watch the Drain: Items sent down the drain have a major impact on septic system performance. Garbage disposals require significant water to move scraps. Once in the tank, some solids break down by bacterial action, but most grindings require pumping. Using a disposal could necessitate more frequent pumping. Composting is a better way to recycle kitchen scraps.
- Care for the Drainfield: The drainfield is a vital component of a septic system.
- Plant only grass over and near the septic system. Roots from nearby trees or shrubs can cause damage.
- Avoid driving or parking vehicles on any part of the septic system to prevent soil compaction and pipe damage.
- Keep roof drains, water softeners, sump pumps, and storm water run-off away from the drainfield. Flooding the drainfield with excessive water slows the treatment process and can cause backups.
How to Identify a Problem:
Obvious signs appear when a sewage system fails. Awareness of these indicators is essential:
- Toilets backing up
- Drains failing to clear
- Excessive moisture or wastewater surfacing over the drainfield
- Foul odors emanating from the drainfield or septic tank
Alert observation helps the community. Report suspicious discharges and failing septic systems. Finding these problems quickly leads to cleaner water for everyone. (810) 987-7253 or 1-877-504-SWIM.
Maintenance Details:
- Tank Location: Lids or manhole covers may be visible; otherwise, contact the Health Department for a drawing of the septic tank and drainfield. The tank can be located by gently tapping a steel rod into the ground starting 10 feet from the point where the pipe leaves the house, or by observing where snow melts first during a light snowfall.
- Additives: Many products such as solvents, yeasts, bacteria, and enzymes claim to improve performance or reduce pumping needs, but significant differences have not been found. Septic tanks already contain the microbes needed for effective treatment. Periodic pumping is a much better way to ensure a safe and effective system.
Additional Resources: