Managing Your Septic System

           Management is the key to a lasting wastewater disposal system.

How Your System Works

  A septic system has two basic parts: a septic tank and soil absorption field or drain field.  Wastes flow from the house into the septic tank.  In the septic tank, most solids are separated to the bottom and are partially decomposed by bacteria to form sludge.  Some solids float and form a scum mat on top of the water.

     The liquid effluent from the septic tank, carrying disease-causing organisms and liquid waste products, is discharged into the soil absorption.

      Here the water is further purified by filtration and decomposition by microorganisms in the soil.  The semi-purified wastewater then percolates to the groundwater system.

Septic System Management 

How the Septic Tank Functions

      The typical septic tank is a large, buried, rectangular, or cylindrical container made of concrete, fiberglass, or polyethylene.  Wastewater from your toilet, bath, kitchen, laundry, etc., flows into the tank.  Heavy solids settle to the bottom where bacterial action partially decomposes them to digested sludge and gases.  Most of the lighter solids, such as fats and grease, rise to the top and form a scum layer. 

Septic tanks may have one or two compartments.  Two compartment tanks do a better job of settings solids and may be required for new systems.  Tees or baffles are provided at the tank's inlet and outlet pipes.  The inlet tee slows the incoming wastes and reduces disturbance of the settled sludge.  The outlet tee keeps the solids or scum in the tank.  All tanks should have accessible covers for checking the condition of the baffles and for pumping both compartments.  If risers extend from the tank to or above the ground surface, they should be secure to prevent accidental entry into the tank. 

      Solids that are not decomposed remain in the septic tank.  If not removed by periodic pumping, solids will accumulate until they eventually overflow into the drain field, leading to costly repairs or replacement.  Remember that retention time, or the time available for solids to settle out of wastewater, decreases as the sludge layer increases in your septic tank.

Maintenance

Most septic tanks must be pumped:

	once every three to five years
	depending on tank size
	number of persons in the household
	whether or not occupants are minimizing release of unnecessary solids into the wastewater

How do I determine when to pump?

     Many homeowners prefer to give this responsibility to a reputable septic tank pumping firm.  They will periodically check your system to determine the rate of solids accumulation and proceed with a pumping schedule designed for your specific situation.  Some homeowners may wish to measure sludge depth and scum thickness themselves, using a homemade probe.  Guidelines for performing this messy operation may be obtained from your local sanitarian in the county health office.  The tank requires pumping if:

A.)  the top of the sludge deposit is within 12 inches of the outlet baffle

B.)  the bottom of the floating scum mat is within three inches of the bottom of the outlet baffle

C.)  the top of the floating scum mat is within one inch of the top of the outlet baffle

D.)  the floating scum mat is more than 10-12 inches thick.

Should I use any special products to enhance the operation of my septic tank?

      Many products which claim to improve septic tank performance or reduce the need for routine pumping are available.  These solvents, yeasts, bacteria, and enzymes have not been found to make a significant difference.  Some can even cause solids to be carried into the drain field, causing early clogging and repair.  Some products contain organic solvents which contribute to groundwater pollution.

Where is my tank located?

      If you do not know where your septic tank is located, you can find it by gently tapping a steel rod into the ground starting about 10 feet from the point where the sanitary drain leaves the house.  Another method is to wait for a light snowfall.  The snow is likely to melt first directly over the septic tank.  

The Drain field

The drain field receives septic tank effluent.  It has a network of perforated pipes laid in gravel-filed trenches (two-three feet wide), or beds (over three feet wide) in the soil.  Wastewater trickles out of the pipes, through the gravel layer, and into the soil.  The size and type of drain field depends upon estimated daily wastewater flow and soil conditions.

      The soil below the drain field provides the final treatment and disposal of the septic tank effluent.  After the effluent has passed into the soil, most of it percolates downward and outward, eventually entering the groundwater.  A small percentage is taken up by plants through their roots, or evaporates from the soil.

      The soil filters effluent as it passes through the pore spaces.  Physical and biological processes treat the effluent before it reaches groundwater, or a restrictive layer, such as hardpan, bedrock, or clay soils.  These processes work best where the soil is somewhat dry, permeable, and contains plenty of oxygen for several feet below the drain field. 

Warning Signs of a Failure

	Odors, surfacing sewage, wet spots or lush vegetation in the drain field area
	Plumbing or septic tank backups
	Slow-draining fixture, not due to local clogging
	Gurgling sounds in the plumbing system

     If you notice any of these signs or if you suspect problems with your septic tank system, contact your local environmental health department.

Shiawassee County Environmental Health Department

201 N. Shiawassee Street

Corunna, Michigan 48817

(989) 743-2392