L-5347 11-07

On-site wastewater treatment systems

Geotextile fabric Sand/loam soil

Gravel Perforated pipe for effluent disposal

Two-compartment Soil absorption field septic tank Figure 1: A septic tank and soil absorption fi eld system. Operation and maintenance Bruce Lesikar Extension Agricultural Engineering Specialist The Texas A&M University System

f your home or business uses an on-site wastewater treatment a system or consult manufacturers’ literature. system, commonly known as a septic system, you need to know how I to operate and maintain the system properly to prevent pollution and A conventional septic system — sewage backups. the most common on-site system— consists of a septic tank and a soil For many years, people in the for treating wastewater. Consequently, absorption fi eld. Wastewater from United States viewed on-site systems it is vital that residents maintain them a home or business fi rst goes to the as a temporary way to manage regularly so that they do not pollute septic tank, an enclosed watertight wastewater for homes until they were the environment and pose health container where solids are separated connected to a centralized sewer hazards to people. from liquid wastes. Microorganisms system. In the past, about 25 percent in the septic tank begin consuming the To understand how to operate and of the U.S. homes used septic systems. organic matter, solids and nutrients in maintain on-site wastewater treatment Now, about 37 percent of the homes the wastewater. systems, it helps to know how they being built have on-site wastewater work and what factors affect them. The wastewater then moves to treatment systems. On-site systems are You may wish to obtain other fact a soil absorption fi eld, also called a now considered a permanent solution sheets in this series for specifi cs on drain fi eld. There, it travels through perforated pipes to a bed of gravel or other similar material, and then into the Riser soil, where microorganisms consume more of the contaminants. Ground surface Depth may vary, but may not exceed 12 inches The water then moves through the unless a riser is installed on each clean-out and 1/2 to 2/3 extends to within 6 inches of the ground surface soil and evaporates, is used by plants or of total tank length moves to groundwater. Inlet 12" Clean-out On-site wastewater treatment systems come in many types and sizes. Liquid Tee fitting Outlet Each one’s operation and maintenance Scum requirements depend on: ✓ The treatment method used to remove 3" Tee fitting Depth: 30" contaminants from the wastewater. (minimum) Tee fitting Alternate tee fitting ✓ The amount, or volume, of waste- water the system must handle. ✓ The strength of the wastewater, or the amount of contaminants Sand/gravel cushion it contains. Wastewater contains Figure 2: A two-compartment septic tank is an enclosed, watertight container where organic mater, solids, nutrients solids are separated from liquid waste. and pathogens (disease-causing microorganisms). A residence has an average strength of wastewater, affect how well your on-site system limestone or gravelly sand, your while businesses such as works. on-site system may need to provide additional treatment before it applies restaurants and convenience stores If you use more water than the wastewater to the soil. If the have high-strength wastewater. average for the size of your house, wastewater is not treated adequately your system can be overloaded with When a house is being built, the before it reaches groundwater, your water, and fail. If you want to be size of its on-site wastewater treatment water well can become contaminated. system is determined by the number of able to use more water than average, bedrooms in the house (square footage) you may need to install an oversized There is one exception to the rule and whether water-conserving fi xtures system. that all the wastewater must be treated on and applied to the property where it will be used. The system chosen is one Your wastewater will be stronger is generated. A cluster system legally that will handle the greatest volume and than average if you use a garbage ties several properties together for strength of wastewater for that size of disposal or operate a bakery or day- treatment and land application of their house. care facility at home. The wastewater wastewater. A cluster system is used may need additional treatment, such On-site systems differ from the only when lot size, lot location, and as with an aerobic treatment unit, sand centralized sewer systems used in soils make other on-site wastewater fi lter or trickling fi lter, to bring it back cities and utility districts. Centralized treatment system alternatives to an average strength or remove most systems collect wastewater from many unacceptable. houses and businesses, averaging of the contaminants. together the amounts and strengths of The site itself is also a Maintenance the wastewater fl ows. The amount of factor. An on-site system is a no- wastewater from houses that use much discharge system, which means and management water is offset by those that use little. that the wastewater must stay on Different types of on-site Sewage from homes and businesses are the property where it is generated. wastewater treatment systems mixed to produce an average strength. All contaminants must be removed require different maintenance In contrast, an on-site wastewater from the wastewater before it moves procedures. However, all systems need treatment system and the soil where through the soil to groundwater. maintenance: Yours will fail if you do not maintain it. Follow the maintenance it is located must be able to treat the If your soil does not treat the instructions provided for the equipment amount and strength of the waste-water wastewater enough, as in problem installed for your system. from that house. Your water-use habits soils such as fractured rock, Karst These general tips can also help disposal fi eld. These solid surfaces wastewater treatment system that you keep your on-site wastewater prevent access to the system for has mechanical components or treatment system operating: maintenance, reduce the ability of alarms. water to evaporate from the soil, ✓ Do not treat an on-site wastewater ✓ Maintain a grass cover over the and restrict air movement into the treatment system as if it were a drain fi eld. Plant warm-season soil. normal centralized sewer system. grasses that use much water Items fl ushed down the toilet ✓ Do not drive heavy equipment and overseed with cool-season do not disappear. They must be over the components of a waste- grasses during the winter. Grasses treated by the on-site wastewater water treatment system. The remove a signifi cant portion of the treatment system. equipment can crush them. The water from a system and the grass components are designed to ✓ Do not use in-sink garbage cover must be maintained. Trees support the soil over the top of grinders excessively or discard also remove water and can be the system, not equipment driving too much grease. Garbage planted around the drain fi eld. over it. grinders can cause sludge or ✓ Divert away from the land scum to build up rapidly, making ✓ Natural bacteria are present in application area any rainwater it necessary to clean the septic the wastewater to decompose the coming off driveways, other system more frequently and waste. Chemical additives are hard surfaces and the roof. The possibly causing it to fail because not necessary for a septic tank land application area is designed the wastewater is too strong for to operate. Some additives may to manage a specifi c amount of the system to handle. even harm the tank’s operation. water. Rainwater could fi ll the Remember: The septic tank is ✓ Do not use the toilet as a trash system, leaving no room for supposed to collect solids. If you can. Do not dispose of cleaning wastewater. Design landscaping to fl ush solids out of the tank and tissues, cigarette butts, diapers carry runoff water away from the into the drain fi eld by adding or other trash in the toilet. This land application area. chemicals, the solids will plug wastes water and loads too many ✓ Excessive wastewater fl ows can the drain fi eld, and you’ll have to solids on the treatment system. overload the on-site wastewater replace it. ✓ Have the septic tank cleaned treatment system. If you wash ✓ Soaps, detergents, bleaches, drain before sludge accumulates all your clothes on one day, cleaners and other household almost to the bottom of the tank’s you could overload the land cleaning materials very seldom outlet device. If sludge or scum application area, causing water to affect the operation of the system. accumulates to this point, solids pond on the ground surface. You However, use these materials will leave the tank with the liquid also could fl ush water through the in moderation. Excessive use and possibly clog the soil in the system, which can carry solids of cleaning materials or using drain fi eld. Sewage will then through the treatment device. continuous disinfectants in the surface or back up into the house ✓ toilet bowl or disinfecting soaps Do not plumb the condensate through the plumbing fi xtures. and detergents may harm the drain from an air conditioning unit ✓ Because it is impractical for an microbes living in the on-site or commercial ice maker into the average homeowner to inspect wastewater treatment system. on-site system. This extra water a septic tank to see if it needs to can overload the system. ✓ If you have a water softener, do be cleaned, establish a regular not send the back-fl ush water into schedule of cleaning the septic Conserve water your on-site wastewater treatment tank every 2 to 3 years. Septic system. You can greatly reduce the tank pumpers are equipped ✓ amount of water entering your on- to clean septic tanks. Only Do not come into contact with the site wastewater treatment system by people registered with the Texas liquid from the on-site wastewater adopting water conservation practices: Natural Resource Conservation treatment system unless it has ✓ Commission may pump and been disinfected. Nondisinfected Because showers usually use transport septic tank sludge. wastewater may contain pathogens less water, take showers instead that could make you sick. of baths. Install a water-saving ✓ Do not build driveways, storage ✓ shower head that uses less than buildings or other structures Do not allow electrical service 2.5 gallons of water per minute. over the treatment works or its to be interrupted to an on-site This practice saves both water and the energy required for the extra of the existing 3.5 gallon or larger Summary hot water. toilet. Do not use bricks, because ✓ On-site wastewater treatment they can crumble and damage the ✓ If you take a bath, don’t fi ll systems are a permanent solution fi xture. Make sure the toilet dam the tub as high as usual. A to our wastewater management does not contact the moving parts whirlpool bathtub requires much needs. However, you cannot in the toilet tank, because this more water. If your home has a treat these systems as if you may allow too much water to fl ow whirlpool tub, make sure your are connected to a centralized down the drain. septic system can accept the sewer because you do not have additional wastewater. ✓ Whenever possible, operate the the averaging effect of being dishwasher with a full load. connected to a system with your ✓ Repair leaky faucets and faulty neighbors. toilet-fi lling mechanisms as ✓ Do not leave the water running quickly as possible. continuously when brushing your ✓ To achieve an average fl ow, teeth, washing your hands, rinsing change your personal habits that ✓ Check toilets for leaks that may kitchen utensils or cleaning send too much water continually not be apparent. To determine if vegetables. or on a single day. there is a leak, add a few drops of food coloring or a leak detection ✓ Use faucet aerators that restrict ✓ Or, install a system that can tablet to the tank. Do not fl ush. If the water fl ow to no more than 2.2 manage more wastewater. color appears in the bowl within a gallons per minute. ✓ Remember that an on-site few minutes, the toilet fi ll or ball- ✓ Keep a container of drinking wastewater system is designed cock valve needs to be adjusted to water in the refrigerator instead of to handle a specifi c volume of prevent water from overfl owing running the faucet until the water organic matter. Placing additional the stand pipe, or the fl apper at turns cool. solids into the system can cause the bottom of the toilet tank needs it to fail. Items fl ushed down the to be replaced. ✓ Insulate all hot-water pipes to drain do not just disappear. The avoid long delays of wasted water ✓ Reduce the amount of water used on-site wastewater treatment while waiting for heated water. for fl ushing the toilet by installing system must treat these items and a new toilet (1.6-gallon) or a ✓ Ask your city, county or local distribute the water into the soil. toilet tank dam. Or you could fi ll government about their programs plastic bottles with water, cap to conserve water and how they them and lower them into the tank can help you save water.

Produced by Agricultural Communications, The Texas A&M University System

On-site Wastewater Treatment Systems series publications can be downloaded free from http://tcebookstore.org Visit Texas Cooperative Extension at: http://texasextension.tamu.edu

Educational programs of the Texas Cooperative Extension are open to all people without regard to race, color, sex, disability, religion, age or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Edward G. Smith, Director, Texas Cooperative Exension, The Texas A&M University System. 5M, Reprint