Septic Systems
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Septic Systems A Buyer’s & Seller’s Guide First American Title Insurance Company of Oregon Created by Tod Hunt, Regional Marketing Manager Education Program Director Jackson & Josephine Counties First American Title Insurance Company of Oregon Medford, Oregon April 2006 Table of Contents How Septic Systems Work pp 1-3 Septic Tank: Wastewater Separation p 2 Drainfield: Wastewater Distribution p 3 Locating System Components p 4 Septic System Inspection & Pumping p 5-7 Inspection Items p 5 Septic Tank Pumping pp 5-6 Septic Tank Inspection p 7 Installing a New System pp 8-19 Permit Process pp 8-10 Site Evaluation pp 8-9 Soil Evaluation pp 9-10 Construction & Installation Considerations pp 11-13 Setback Requirements p 12 Drainfield Construction pp 13-14 Sand Filter Systems pp 15-18 Alternative Treatment Technology pp 18-19 Preventative Maintenance pp 24-28 Control Water Usage p 20 Drainfield Care pp 21-22 Pools, Spas, Runoff & Softener Issues pp 22-24 Stream Crossings p 24 System Alterations p 24 System Failure & Repair pp 25-27 Signs of Septic System Failure p 25 Causes for System Failure pp 25-7 System Repair p 27 Contractors pp 28-29 Site Development Plan Samples pp 30-32 Index p 33 Acknowledgments p 34 SEPTIC SYSTEMS How Septic Systems Work Owning a Private Sewer System Do you know where the water goes when you empty a sink or flush a toilet? If your home is in a city, the wastewater goes into a municipal sewer system and to a sewage treatment plant. If your home is in a rural area or a small community, chances are your wastewater goes to your own private septic system. A septic system treats and disposes of your sewage right in your own yard. The septic system, if properly sited and when performing properly, safely treats and disposes of your sewage without creating any danger to your health or to the environment. Normally you don't have to worry about sewage in your yard. However, if the septic system is not functioning properly, there can be health concerns. Therefore, it is a good idea to understand how a septic system works and what you can do to make sure it continues to work properly. How A Septic System Works The purpose of on-site disposal systems is to provide for the treatment of household waste using natural processes. A septic system with an absorption field is the most common method for treating waste from a rural residence. A typical septic system has three main components: 1. a plumbing collection system 2. a septic tank well 3. a drainfield 100 ft. Plumbing: Wastewater Collection All wastewater containing human wastes, nutrients, septic tank dirt, and other contaminants must be collected and delivered to the septic tank and drainfield for diversion box treatment and disposal. All water used in bathing, toilets, laundry, and dishwashing must be treated by the system. Drains allowing wastewater to enter the system should be equipped with strainers and other filtration devices to reduce the amount of food replacement particles, hair, and lint entering the system. area soil absorption system Some older homes may have been plumbed to bypass the septic tank with wash water but this has proven unsuccessful and damaging to drainfields. Oregon's rules require all wastewater to be treated. However, water from roof drains, basement drainage sump pumps, hot tubs, and swimming pools should not be put into the septic system. These large volumes of “clean water” will overload the system. Original and remodeled plumbing systems must be correctly designed and installed to allow trouble-free operation. Before remodeling, consider the impact of changes on the septic system. FIRST AMERICAN TITLE 1 SEPTIC SYSTEMS How Septic Systems Work Septic Tank: Wastewater Separation The purpose of the septic tank is to separate the solids from the liquids in the wastewater stream and to begin the process of breaking down contaminants. The tank is a buried, watertight container typically constructed of concrete, steel, fiberglass or polyethylene and can range in size from about 1,000 to 1,500 gallons or more. To give you an idea of how large this is, consider that up to 50 gal- lons of water fit in a standard bathtub and ordinary toilets use up to 3.5 gallons per flush. So, de- pending on the size of your household, it doesn't take too long to fill the septic tank. Two-chamber septic tank Most septic tanks have just one interior chamber into which the wastewater from your house enters; though a 2-chamber system will process influent more efficiently. When the influent enters the first chamber, its velocity slows so that the heavier solids can settle out of the water into the bottom of the chamber, and lighter materials can float to the surface. The accumulation of settled solids at the bottom of the tank is called sludge and the lighter solids (greases, fats and soaps) which form a mass on Courtesy of Landmark Inspection Service the surface of the liquid in the septic tank is called scum. In between the sludge and the scum is liquid waste or wastewater. Micro-organisms, like bacteria, and other natural processes act to decompose the waste materials in the liquid waste. Incoming water should be held in the tank for at least 24 hours in order to improve settling. Up to 50 percent of the solids will decompose into liquids and gases. Sludge and scum are also digested and compacted into a smaller volume. This is the first step in the process of purifying your household wastewater. When the first chamber of the tank becomes filled, the liquid waste begins to fill the second chamber. The chambers of the septic tank are designed to prevent the movement of sludge and scum to the second chamber, allowing only the movement of liquid. Once the second chamber is filled, and more influent enters the first chamber, an equal amount of the partly-treated liquid waste flows into the second chamber, while an equal amount flows out of the second chamber into the leaching bed or drainfield. The water flowing out into the leaching bed is called effluent. This is often referred to as primary treatment. Pathogens in the waste are NOT destroyed in the septic tank. Bacteria in the septic tank prepare the wastewater for final treatment in the drainfield. The separate chambers, a T-shaped outlet, and often screens in the septic tank prevent sludge and scum from leaving the tank and traveling into the drainfield area. Biological and chemical additives are not needed to aid or accelerate settling or decomposition. As a general rule, no solids other than human wastes and toilet paper should be flushed. FIRST AMERICAN TITLE 2 SEPTIC SYSTEMS How Septic Systems Work The Drainfield: Wastewater Distribution The majority of the treatment of the wastewater occurs in the drainfield. A gridwork of perforated pipes or clay tiles in the leaching bed area evenly distributes the effluent over the natural soil or imported fill. Sometimes a distribution tank is used at the head of the pipes to more evenly distribute the effluent to the pipes. Gravel supports and forms an envelope around the pipe, to protect it from roots and burrowing animals. The perforations in the pipe allow the effluent to escape to the soil. Uncompacted, unsaturated, undisturbed soil must surround the soil treatment system. This system, typically referred to as secondary treatment, may be a series of trenches or a mound. As the effluent filters through the soil, micro- organisms in the soil digest and remove the remaining impurities (such as suspended solids, organic chemicals and viruses and/or bacteria). There are millions of naturally-occurring beneficial microscopic organisms in every tablespoon of soil that kill disease-causing organisms in the sewage and remove nutrients. These beneficial bacteria in the soil need air to live. Therefore, a zone of unsaturated soil must be present below the drainfield for complete treatment. A biomat, or thin layer of fine solids, dead bacteria, and soil bacteria forms where the sewage meets the soil. This biomat layer regulates how fast liquid passes out of the trench or bed into the soil so the soil beneath the trench remains unsaturated. Once the wastewater is through the biomat layer and three feet of unsaturated soil, many harmful pathogens have been destroyed. Eventually, the purified water reaches the groundwater. Courtesy of Landmark Inspection Service If a soil has a high permeability or high water table, the effluent can reach the groundwater before it is fully treated. To avoid this, a shallow trench or mound system design is sometimes used. Both usually require a hydraulic pump to ensure uniform distribution of effluent over a field. As you can see, the operation of your septic system is fairly automatic and can work quite well by itself with very little maintenance required by the homeowner. Note the key words though, “little maintenance”, not “no maintenance”. FIRST AMERICAN TITLE 3 SEPTIC SYSTEMS Locating Your System Components Finding Your System Most people have never seen their septic system, and if the system is properly maintained, most may never need to see it. A septic system is generally composed of two main parts: a watertight septic tank and a network of perforated pipes, called a tile bed, leaching bed or drainfield. All these parts are buried under your lawn so you may not even be aware of them. Yet, your septic system receives all the wastewater from your house, including toilets, showers, sinks, dishwasher, washing machine, etc. and purifies that water so it is safe to re-enter the ground water system.