Septic systems explained

Septic systems are individual wastewater treatment systems that use the soil to treat small wastewater flows, usually from individual homes.

There are many types of septic systems in use today. While all septic systems are individually designed for each site, most septic systems are based on the same principles.

A septic system consists of a septic tank, a distribution box and a drainfield, all connected by pipes, called conveyance lines.

Your septic system treats your household wastewater by temporarily holding it in the septic tank where heavy solids and lighter scum are allowed to separate from the wastewater. This separation process is known as primary treatment. The solids stored in the tank are decomposed by bacteria and later removed, along with the lighter scum, by a professional septic tank pumper.

After the partially treated wastewater leaves the tank, it flows into a distribution box, which separates this flow evenly into a network of drainfield trenches. Drainage holes at the bottom of each line allow the wastewater to drain into gravel trenches for temporary storage. This effluent then slowly seeps into the subsurface soil where it is further treated and purified (secondary treatment).


Septic system dos and don'ts


DO have your tank inspected and pumped out every three to five years by a licensed septic hauler.

DO keep a record of pumping, inspections, and maintenance.

DO practice water conservation to reduce the amount of water going into the septic system.  Repair dripping faucets and leaking toilets.  Run washing machines and diswashers only when full.  Avoid long showers.  Consider replacing plumbing fixtures with water-saving features.

DO learn the location of your septic system.  Avoid constructing patios, decks, and paved surfaces over your system.

DO divert roof drains and surface water from your system.  Keep sump pump water and house footing drains away from the septic system.

DO take leftover household hazardous chemicals to a TOX DROP location (327-4TOX) and avoid dumping these products into your system.  Use typical household cleaners (bleach, disinfectants, drain cleaners) and follow label directions.

DO be sure to have a healthy grass cover on the absorption field area, but avoid planting shrubs and trees as the roots can damage the septic system tiles.

DON'T allow anyone to drive or park on any part of your system.

DON'T make repairs to your system without obtaining a permit from the Marion County Health Department.

DON'T use septic tank additives.  These products usually do not help and some contain chemicals that can hurt your system or pollute the environment.  Human sewage has plenty of microorganisms to do the job of breaking down sludge!

DON'T use your septic system as a trash can.  Avoid flushing into your septic system grease, disposable diapers, plastics, cigarette butts, excessive toilet paper, kitty litter, tampons, condoms --- you get the idea!  These items do not degrade and will fill up the tank quickly, costing you more in pumping fees or allowing sludge to clog the absorption field.


For more information, please call the Marion County Health Department Water Quality and Hazardous Materials Program at (317) 221-2266.

Resource: Your Septic System: A Reference Guide for Homeowners, (published 1990) from the Northern Virginia Regional Commission.