Septic Tank Maintenance & Operation
This article was published in the Houston Daily Journal on February 20, 2008.
Households not served by public sewers depend on a septic systems to dispose of wastewater. There are many different types of septic systems designed to fit a wide range of soil and site conditions. The most common is the conventional septic system consisting of two main parts: the septic tank and the soil drain field.
A septic tank is a large, underground, watertight container, typically about 9 feet long, 4-5 feet wide and 5 feet tall, that is connected to the home’s sewer line. While typically designed with a 1,000 gallon liquid capacity, the size of the tank is determined by the number of bedrooms in the home. Septic tanks may be rectangular or cylindrical and may be made of concrete, fiberglass or polyethylene.
Raw wastewater from the home’s fixtures flows into the tank where the solids separate from the liquid. Light solids, such as soap suds and fat, float to the top and form a scum layer. This layer remains on top and gradually thickens until you have the tank cleaned. The liquid waste goes into the drain field, while the heavier solids settle to the bottom of the tank where they are gradually decomposed by bacteria. But some non-decomposed solids remain, forming a sludge layer that eventually must be pumped out.
Septic tanks may have one or two compartments. Two-compartment tanks do a better job of settling the solids and are required in all new installations. Tee or baffles at the tank’s inlet pipe slow the incoming wastes and reduce disturbance of the settled sludge. A tee or baffle at the outlet keeps the solids or scum in the tank and prevents their entrance into the drain field. All tanks should have accessible covers for checking the condition of the baffles and for pumping both compartments.
Further treatment of wastewater occurs in the soil beneath the drain field. The drain field consists of long underground perforated pipes connected to the septic tank. The network of pipes is typically laid in gravel-filled trenches. Liquid waste or effluent flows out of the tank and is evenly distributed into the soil through the piping system. 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 the effluent as it passes through the pore spaces. Biological processes treat the effluent before it reaches groundwater, or a restrictive layer. The size and type of drain field depends on the estimated daily wastewater flow and soil conditions.
Even a properly designed and installed septic system cannot treat wastewater if the tank is not used and maintained properly. Here are a few tips for using your septic system:
- Pump the tank every 3-5 years until your own personal use pattern is determined. The more people using a system, the faster the solids will accumulate in the tank, and the more frequent the pumping will need to be. If the tank gets too full, particles of scum or sludge may be pushed out of the tank. This material will clog the drain lines and cause the septic system to fail. The Health Department can also provide you with a recommended pumping schedule depending on the size of your tank and the number of people in your home.
- Conserve water. Fix leaks and drips. If you replace old fixtures, install new “low flow” types. Use low flush toilets, faucets, and washing machines. For example, up to 53 gallons of water is discharged into your system with each load of laundry from the standard machine.
- The use of a garbage disposal increases the load of solids into the tank by 50% requiring even more frequent pumping. Though allowed, garbage disposals are not recommended.
- Do not pour fats and oils down the drain and other non-biodegradable items. They can build up and clog the septic tank pipes.
- Put paper towels, tissue, cigarette butts, disposable diapers, sanitary napkins, and other material in the trash can, not the toilet. You do not need to add any commercial products or yeast to your system. Additives do not improve how well your system works. In fact, additives can damage your system by breaking up the sludge and scum layers, causing them to flush out of the tank and clog the infiltration bed.
- Use normal amounts of detergents, bleaches, drain cleaners, household cleaners and other products. Liquid detergents are recommended over powder. Avoid dumping solvents like dry cleaning fluid, paint thinner, or auto products down the drain.
- Direct gutter down-spouts and water runoff away from the septic tank and drain field to avoid saturating the area with excess water.
- Dense grass cover and other shallow rooted plants are beneficial over a septic field. However, do not plant trees because large plant roots can clog or break the pipes.
- Avoid compacting the soil over the infiltration area. Do not drive or park vehicles over the area. These activities can also crack pipes or cause the distribution box to settle unevenly, meaning the effluent will only flow into part of the drain field.
Other helpful information, such as educational DVDs and pamphlets, are available at the Health Department upon request. For more information, call (478) 218-2020.
Submitted by Clarence Johnson
Environmental Health Specialist III
Houston County Health Department