Septic Tank System Users Guide*

Operating and Maintaining Your System

If you own a septic tank system you are an operator of a highly efficient wastewater treatment system! A properly designed, constructed and operated septic tank system treats your wastewater more completely than a conventional municipal treatment plant and returns it safely to the ground water resource. Your system represents a significant investment that you will want to protect. Proper operation and regular maintenance will increase its life and effectiveness. Use this guide to understand how to properly care for your onsite wastewater treatment system.

How your system works

An onsite wastewater treatment system typically consists of a septic tank and subsurface infiltration field or drainfield. It is designed to treat both black water (toilet wastes) and gray water (wastewater from sinks, baths, laundry and water softener brines) so that they may be safely discharged to the soil for recharge to the ground water.

The septic tank

When wastewater is discharged from your home, it enters the septic tank. This tank provides partial treatment of the wastewater. It is a watertight tank that holds the wastewater for up to a day or more. During this time, solid particles suspended in the wastewater are removed. Heavier solids settle to the bottom of the tank to form a sludge layer. Buoyant solids such as greases and oils float to the top to form a scum layer. If not removed, these solids could clog the infiltration field.

The sludge and scum are stored in the tank and undergo digestion or reduction in volume by facultative and anaerobic microorganisms that can thrive without oxygen.

In the process, methane, carbon dioxide, hydrogen sulfide and other gases are released that are vented from the tank through the plumbing stack vent on your house roof. Only about 40% of the sludge and scum volume can be reduced through digestion so the contents of the tank must be pumped periodically and disposed of at a treatment plant or licensed land spreading site.

The subsurface infiltration field (Drainfield)

The subsurface infiltration field absorbs the septic tank effluent and completes the treatment as the liquid percolates through the soil to the ground water. The field typically consists of a series of trenches or a bed. They are excavations in permeable soil that have been partially filled with large gravel. A perforated pipe is buried in the gravel to distribute the septic tank effluent onto the infiltrative surface of the soil. The gravel is covered with natural soil.

Other subsurface infiltration fields may be used for different site characteristics. At-grades and mounds are similar infiltration fields except that they are built on or above the natural soil surface. They provide additional soil materials where there is insufficient depth of unsaturated soil to insure satisfactory treatment.

The infiltration system provides excellent treatment. The soil acts as a biological filter that removes nearly all harmful parasites, bacterial and viruses. It is also very effective in removing toxic organics that may be in the wastewater from household cleaning products. It will not remove nitrate nitrogen, however. Elevated nitrates in the ground water can raise health concerns if found in wells used for drinking water supplies. However, agricultural practices are usually the source of the nitrates rather than properly silted onsite treatment systems.

Taking care of your system

Proper care and regular maintenance will increase the effectiveness and life of your system. The two most important things you can do are to use water wisely and regularly pump your septic tank. Some helpful suggestions are provided below.

  • Conserve water

    • The less water you use, the less wastewater your system must treat
    • Repair leaking faucets and toilets immediately
    • Wash only full loads of laundry and wash throughout the week rather than on one day
    • Use low volume flush toilets and water conserving showerheads
    • Limit your automatic water softener regeneration cycle frequency

  • Eliminate Clear Water

    • Clear water is rainwater, snowmelt or other clean water that does not belong in your system
    • Pump foundation drains into the yard, not into your septic tank
    • Direct gutter downspouts away from your system
    • Grade your yard so surface runoff is directed away from your system

  • Minimize Waste

    • Do not put anything down the drain that could be disposed of some other way
    • Do not flush disposal diapers, sanitary napkins, tampons, condoms, paper towels, cigarettes or other non-degradable products into your system
    • Avoid pouring grease, sauces, gravies, etc. down the drain
    • Limit the use of your garbage grinder
    • Do not dispose of oils, paints, paint thinners, brush cleaners or other harmful chemicals into your system
    • Septic tank additives such as enzymes, bacterial preparations, degreasers, etc. are not necessary for a well functioning system

  • Pump and inspect septic your tank

    • The more you put into your tank, the more frequently it will need to be pumped. Under normal use, pumping frequencies range from 2 to 3 years
    • Hire a licensed pumper to inspect and pump your tank every three years
    • Have your tank inspected for leaks, cracks and broken baffles when it is pumped
    • Do not enter the septic tank because the gases in the tank are dangerous and potentially lethal

  • Protect the drain field

    • Protect your drain field from damage because if it fails, it may have to be replaced
    • Prevent driving over the field, building over it or compacting the soil in any way
    • Plant only grass over the field
    • Check inspection pipes monthly for standing water

  • Keep accurate records

    • Records of your system are important for scheduling timely maintenance and trouble shooting problems
    • Keep a drawing of your system showing exact locations of tanks and infiltration field
    • Record of septage pumping
    • Description of problems and repairs

What to do when there is a problem

If your toilet does not seem to flush properly, your drains are backing up or you notice wastewater on the ground surface you have symptoms of a hydraulic failure. When you first notice any of these, do the following:

Eliminate all unnecessary water use immediately
Call a licensed pumper to pump the tank and empty the infiltration field if possible
Hire a professional to advise you of appropriate corrective measures
*This information is provided courtesy of the Cass County Minnesota Environmental Services Department.