Printed on Mar 01, 2015 @ 12:52 PM
This document outlines the principles of septic system operation and explains the maintenance procedures necessary to prolong the life of the system. If neglected, the septic system can fail and lead to potential health hazards. If properly operated and maintained, the system can provide many years of trouble-free service.
The standard household septic system is a two part sewage treatment and disposal system buried in the ground. It consists of a septic tank and disposal field.
Household sewage is a combination of wastewater from several sources, including sinks, showers, washing machines, garbage grinders, and dishwashers. The largest source of sewage is the toilet.
The Septic Tank
Untreated household sewage will quickly clog all but the most porous gravels if applied directly to the soil. The function of the septic tank is to allow separation of the solids from the sewage so that the remaining liquid (effluent) can be absorbed into the ground without clogging the soil. Within the tank three important processes take place. The heavier solid particles in the sewage settle to the bottom of the tank, forming a layer of sludge. Lighter materials, including fats and grease, float to the surface and form a scum layer. Bacteria (called anaerobes, because they live without oxygen) live in the septic tank and slowly digest some of the solids into gaseous and liquid components. This helps to reduce sludge build up.
Sludge and scum are stored within the tank rather than being allowed to flow into the disposal field where they would quickly clog the soil and cause the system to fail prematurely. As the tank fills with sludge and grease, efficiency of treatment decreases. Sludge and scum are removed when a septic tank is pumped.
The Disposal Field
The disposal field generally consists of a network of perforated pipes laid in gravel-filled trenches. After partial treatment in the septic tank, the sewage effluent flows into the distribution box or a series of drop boxes, then out through the perforated pipe and into the gravel-filled trenches. The gravel acts as a media for aerobic bacteria and other organisms to feed on the sewage.
In the soil below the disposal trenches, solid particles and disease causing bacteria are filtered out. Soil bacteria destroy many of the toxins and pollutants while other toxins and pollutants become bonded to clay particles. While these mechanisms remove many pollutants, some trace constituents such as Nitrates may reach groundwater tables.
In order to take proper care of a system the homeowner must know where it is located. If the septic tank's access manhole is at ground level, it should be easy to locate. Most access manholes are buried somewhere under the lawn or garden. To locate the septic tank, look under the house or in the basement to find where and in what direction the sewer pipe goes out. Septic tank locations are sometimes indicated by either lush or stunted grass growth, and /or mounded or depressed areas which differ from the rest of the yard. Any likely spot can be probed with a metal rod. A tank installed under current rules should be a minimum of five feet from the house foundation. Most systems installed since 1992 have tracer wire from the foundation to the tank and to the first box.
If this doesn't work, ask someone who may have seen the system installed or pumped (a neighbor, the builder, or a previous owner). Benton County Environmental Health Office has records showing the location of most newer septic systems. The more recent the installation the more likely we are to have the record. The installation records of increasingly older systems may be incomplete or nonexistent. If all else fails, turn the job over to a local septic tank pumper.
Once the tank has been located it should be permanently marked with a stake or flagstone and its location should be recorded in your files.
Don't wait until your system shows signs of failure to have your septic tank pumped. The recommended pumping interval is every three to five years. You must call a licensed pumper to do the work. Proper pumping equipment will clean out scum, sludge, and all liquid. The pumped sewage will be disposed of at an approved facility. A thorough pumping service should also include an inspection of the inlet and outlet fittings, and the overall integrity of the tank.
A licensed pumper is assigned an official license number from the Department of Environmental Quality (DEQ). The license number should be given to you upon request and can be verified through the Environmental Health Office. The Environmental Health Office has a list of local licensed pumpers, or you can consult the Yellow Pages of your telephone directory.
It is not necessary to leave any of the sludge in the tank as "seed." Incoming sewage contains all the bacteria needed for proper operation.
The use of enzymes and other additives has not been shown to be of significant value. While their use may not harm the system, some may pose environmental hazards to the disposal field area or ground water. They do not take the place of regular maintenance.
Septic systems generally give little warning that they are about to fail. However, the following symptoms often indicate that the system is becoming clogged:
If the sewage effluent cannot be absorbed into the soil near the disposal field, sewage will backup and overflow onto the surface of the ground or inside the dwelling. There are four major causes of this problem:
Should any of the symptoms that indicate system failure appear, do the following:
Contact the Environmental Health Office. An Environmental Health Specialist can visit your property to assess the situation. Repairs may not be warranted or only minor repairs or improvements may be needed. However, in most cases the disposal field must be replaced with a new one.
Pump the tank regularly, every three to five years. Sludge build up varies with each family. Ask what frequency your pumper recommends. Do not wait until failure symptoms show up.
To protect your septic system against premature failure follow these simple procedures:
Benton County Environmental Health works to protect us against environmental factors that may adversely impact human health or the ecological balances essential to long-term human health and environmental quality, whether in the natural or man-made environment.