General Overview of a Septic System

A septic system is an onsite sewage treatment and disposal facility. It consists of three main parts: the septic tank, the drainfield and the soil under the drainfield. A septic system should effectively accept and treat liquid wastes from your home. Its ultimate purpose is to prevent contaminants from entering the groundwater and nearby wells, lakes and streams. Installing a new conventional septic system can cost from $7,000 - $10,000+/-. Alternative systems may cost in the range of $10,000 - $20,000 . . . or more. In Arizona, an estimated one of every five households is served by some type of onsite wastewater system. Savvy homeowners understand that system problems are cheaper and easier to prevent than they are to correct. They are also aware that a well maintained system can enhance the value of their property. SYSTEM RECORDS: Your property record file should include copies of your system’s permitting documents and plot plan. These documents will be a valuable reference to help you better understand the components and location of your system. They will also save time for the inspector or service provider of your system. RECOMMENDATION: If you do not already have system records in your possession, contact your local Environmental or Health Agency and request copies of all available documents, usually filed by your Tax Parcel Number (APN).

The septic tank provides the first step in treatment using natural processes to partially treat the wastewater. Its primary purpose is to protect the drainfield and the receiving soil from being clogged by suspended solids in the effluent. The wastewater discharged from the home flows into the tank where heavier solids settle to the bottom to form a sludge layer. Lighter materials such as soaps, fats, grease, etc., float to the top forming a scum layer. Micro organisms (naturally occurring bacteria in the waste stream) digest or break down the waste solids helping to reduce the volume of sludge and scum. This biological process can only reduce about 40% of the sludge and scum. The tank must be pumped regularly to remove the accumulated solids. This will prevent them from being washed out into the drainfield where they can clog the soil and create potential system failure. A septic tank is a large watertight container buried in the ground outside of the home. It provides the primary level of wastewater treatment. Tanks are usually constructed of concrete, fiberglass, polyethylene or plastic. Tank size (in gallons) will vary depending on the system’s design requirements. 

A septic system’s drainfield (aka “disposal works” or “leachfield”) delivers the liquid sewage effluent to the soil for final treatment. The effluent flows (by gravity) out of the tank through the outlet baffle/tee (or filter, if installed), into perforated pipe in the drainfield trenches. The effluent passes through holes in the pipe, then trickles through gravel (or other media) to the soil. The soil acts as a biological filter to remove nearly all harmful substances including disease-causing bacteria, viruses and toxic organic materials. A drainfield can consist of a single trench or multiple trenches, as illustrated, depending upon design requirements. If the drainfield is overloaded with too much wastewater in a short period of time, (e.g. running consecutive loads of laundry), it can cause sewage to ooze up to the ground surface. This condition not only creates a health hazard... it can also result in b a c k - u p s a n d o t h e r unpleasant events.