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I.
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PURPOSE
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This information is provided by:
Connecticut Department of Health
Connecticut Environmental Health Association
Connecticut Septic Inspection
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Frequently prospective buyers of a single family home have many questions regarding the septic system serving the dwelling: What does the existing septic system consist of? Is it working properly? How long will it last? If it fails, how much will a replacement system cost?
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The "Connecticut Recommended Minimum Existing Septic System Inspection Form", if utilized by a qualified inspector (see below), could answer many of the above questions. In order for a buyer who is not familiar with the operation and proper maintenance of a septic system to understand the terminology made in the inspection report, the following fact sheet has been prepared.
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II.
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GLOSSARY OF TERMS REGARDING...
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SYSTEM SIZING
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Water Usage: The amount of wastewater that is anticipated will be discharged into the system each day. For residential dwellings it is assumed that each occupant will discharge an average of 50 gallons per day (GPD). Under normal circumstances not more than two people would occupy any bedroom; therefore, a maximum of 100 GPD usage has been set for each bedroom for sizing the system per code. For other uses, such as, office / retail, restaurant, industrial, etc., the water usage would be determined on a case by case basis.
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Number of Bedrooms: The number of potential bedrooms in a home determine the maximum occupancy for that home. This, in turn, will determine the size of the leaching system based on this maximum occupancy assumption. It is not possible for anyone to foresee future utilization of a home over and above the present occupants. It is for that reason that reductions in leaching system size are not allowed even though the present owners may not be using all the potential bedrooms as bedrooms (they may be using rooms as studies, or sewing rooms, or computer rooms, etc.) or occupying each room with two people.
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Application Area: The size of a leaching system is determined by relating the percolation rate of the soil and the anticipated daily discharge to the amount of sewage application area provided by the system. The application area is sometimes referred to as the "wetted perimeter". It is the actual surface area to which sewage comes in contact with just prior to entering the surrounding soil. In a normal system, the "wetted perimeter" forms a biological slime layer that slows down and actually renovates the sewage prior to it entering the surrounding soils. The thickness, and therefore, the speed this layer releases sewage through it, will be dependent on how much suspended solids and greases are released by the septic tank. That is why it is so important to clean the septic tank out periodically to maintain a uniform quality effluent leaving the tank. Each type of leaching system (see Leaching System Section) provides different amounts of "wetted perimeter" per linear foot of system length. Additionally, the type of sewage interface affects the speed in which sewage will pass. Therefore, systems with direct application will be credited higher than systems that have stone / soil interfaces or fabric / soil interfaces. That is why the code assigns different Effective Leaching Credits to each type of leaching product in order to size the system properly.
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SEPTIC TANK
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Purpose of Septic Tank: The septic tank's function is to slow down discharges from the building's plumbing fixtures so that solid material can fall to the bottom of the tank and greases and scum can rise to the top. (See drawing.) A stable biological system within the tank promotes the conversion of organic solids to soluble organic chemicals and gases. The result is a relatively uniform quality septage that will proceed to the leaching fields. There is no need to introduce any commercial additives to the tank to promote biological growth.
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Pump-Out Frequency: It is recommended that septic tanks be cleaned every 2 to 5 years. The frequency should be based on the occupancy of the home and how quickly solid material builds up in the tank. It should be noted that the use of a garbage disposal significantly increases solid material and greases to a tank and therefore, should result in more frequent pumping.
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Volume of Tank: the Public Health Code requires a minimum 1,000 gallon septic tank for all new buildings. For residential buildings an additional 250 gallons of capacity shall be added for each bedroom over three (3). Therefore, a four (4) bedroom home would require a 1,250 gallon tank, a five (5) bedroom home a 1,500 gallon tank, etc. If an older house has a septic tank which falls below the present sizing requirements, it does not have to be replaced (unless physically damaged in some way), but may have to be cleaned more often.
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Inlet and Outlet Baffles / Compartment Wall: In order to further reduce the flow of septage through the tank, baffles are placed on the inlet and outlet piping to and from the tank. In most cases, the baffles consist of "tee" connections of 4" PVC piping. The piping is submerged into septic liquid a minimum of 8" at the inlet and 10" at the outlet. On all new tanks a compartment wall is installed in order to separate the liquid in the tank into 2/3, 1/3 volumes. The septage in the tank passes from the first compartment to the second through a mid-depth opening.
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Outlet Effluent Filter: As of July 1, 2000, all newly installed septic tanks shall have an effluent filter placed at the outlet in place of the outlet baffle. The purpose of the filter is to trap suspended solids that are not heavy enough nor have had time enough to sink to the bottom of the tank (as in a tank that hasn't been pumped in a timely manner and has significant amounts of material that reduces its effective volume). Filters must be periodically cleaned so that they do not plug and back septage back into the house. The cleaning interval should correspond to the recommended pump-out frequency. If the filter plugs at a higher frequency the options would be to change the type of filter presently being utilized (increasing the flow through surface area) or, add additional filters in series to increase the time interval between cleanings.
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SUITABLE SOIL CONDITIONS
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Percolation Tests: In order for a septic system to function properly the soils in which it is placed must be permeable. The quicker water can pass through the soil the smaller the leaching system can be. The percolation test is an empirical means utilized to estimate a soil's general permeability. Unit of measure is in "minutes per inch", representing how long it takes for an inch of water to drop in a small diameter hole, set in the soil strata that will be utilized for sewage disposal.
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Suitable Soils: Soils which are permeable (percolation rates faster than 60 minutes per inch) must meet other criteria prior to being deemed suitable. There must be at least 24" of permeable naturally occurring soils over ledge rock. In shallow bedrock areas substantial amounts of "select" (good quality) fill material would be necessary to raise the leaching system at least four (4) feet above the ledge. Also, the soil in the leaching area must not flood from seasonal high groundwater. The code requires at least 18" of unsaturated soils be present during the wettest time of the year.
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Naturally Occurring Soils: The code refers to a septic system being able to adequately absorb or disperse the expected amount of sewage into the surrounding naturally occurring soils without overflow, breakout or detrimental effect. Discharging a large amount of sewage in a confined area, especially if ground conditions cannot support a great deal of extra water, could overload that area and lead to a septic overflow. Bringing in fill in order to raise the area to keep the "sewage underground" is not a permitted use under the code. The only time such a practice is used is during repair situations where the existing soil conditions cannot absorb and disperse the daily discharge from the building. Not filling, in such a case, would increase the risk of future overflows and health hazards. So in this context fill material (brought onto the site by artificial means) can never be classified as "naturally occurring soils" since the material was not deposited on the site by natural means. The underlying soil would remain limited in its ability to absorb and disperse water. Breakout of sewage (after being partially treated in the fill material) would likely occur where the fill section ends.
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Minimum Leaching System Spread (MLSS): In order to prevent the overflow or breakout of sewage from occurring within or downgrade of a leaching system, the Public Health Code stipulates that the system must be spread out a minimum amount. The calculation of this length is determined by use of tables referred to at "Minimum Leaching System Spread" Factor Tables or by a formal hydraulic analysis. The greater the depth of unsaturated naturally occurring soil, the greater the slope of the ground and the faster the percolation rate will result in reduced system spreads. When a site has only limited amount of area to spread the system the number of bedrooms for the proposed house may have to be reduced to meet MLSS requirements.
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LEACHING SYSTEMS
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Trenches: Are linear excavations that are a maximum of 48" in width and 18" in height. Trenches are backfilled with one-inch stone containing a 4" perforated distribution pipe located 6" or 12" above the bottom of the trench. The distribution pipe is covered with a minimum 2" of stone.
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Galleries: Are hollow structures that are a minimum 48" in width and of various heights (12" up to 48"). Originally these structures were made of concrete, but today plastic structures are available either in single or multiple unit configurations. All galleries are installed with 12" of one-inch stone on each side requiring a minimum six (6) foot wide excavation.
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Pits: Are hollow structures that are placed usually in deep round excavations. The structures are between five (5) feet and ten(10) feet in diameter. Pits are installed with 12" to 24" of one-inch stone surrounding the units. Pits are usually installed only when groundwater levels are very low and the soil in the area has a relatively fast percolation rate.
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Proprietary Leaching Systems: Are various types of leaching products that combine different materials, such as, plastic, filter fabric, and cardboard, into configurations which either eliminates the need for stone, reduces the amount of "select fill" needed, or provides more Effective Leaching Credit per foot than more traditional products listed above.
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ACCESSORY ELEMENTS
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Curtain Drains: In some cases groundwater levels on a site may be too high to install a sewage disposal system properly. If conditions permit, a curtain drain can be installed up hill from the proposed septic area in order to lower groundwater levels. Curtain drains are not always effective in lowering groundwater levels. Therefore, before a leaching system can be installed, springtime monitoring of the area is needed in order to determine the lower water table levels.
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Backwash from Water Treatment System: The Public Health Code - Technical Standards prohibits backwash from a water treatment system from being discharged into a septic system (usually by connecting the discharge hose to the sewer line leading to the septic tank). The Department of Environmental Protection (DEP) is presently developing protocols for the proper disposal of such waste.
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PERMIT TO DISCHARGE
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Permit to Discharge: After completing the installation of any subsurface sewage disposal system (new or repair) a Permit to Discharge shall be issued by the local health department. The issuance of the Permit to Discharge shall imply that an "as-built drawing" has been provided indicating the location of all key elements of the system, the system has been installed in accordance with code requirements (unless specific exceptions to the code are granted in the case of repaired systems) and list any limits that have been placed on the use of the system (such as, limiting the amount of daily discharge to the system).
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III.
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OVERVIEW OF SUBSURFACE SEWAGE DISPOSAL SYSTEM
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The purpose of a home's subsurface sewage disposal system (septic system) is to dispose of the wastewater generated by the occupants in such a manner that the soils on the property can disperse it without causing an adverse effect on groundwater and in turn on public health and the environment. To accomplish this a system consists of the following elements: (1) A sewer line which connects the home's plumbing to the septic tank; (2) A septic tank which allows for the settling of solids and provides the initial treatment of the sewage. This is where waste material is broken down by bacterial action. A properly functioning septic tank will reduce pollutant levels and produce an effluent of fairly uniform quality. This is accomplished by providing inlet and outlet baffles to reduce the velocity of liquid moving through the tank. New tanks (installed since January, 1991) consist of two compartments in order to be even more effective in reducing flows to meet the above objective; (3) A distribution system that directs the flow of effluent from the septic tank to the drainage system in such a manner to insure full utilization of the system. Most systems are "gravity" systems, meaning the flow runs through piping and distribution boxes without the assistance of any mechanical device, such as a pump or siphon; (4) A drainage (leaching) system which disperses the sewage effluent into the surrounding natural soils. There are many types of drainage systems. The specific type utilized on a particular property is usually dependent on the soil conditions that exist on the site. Most residential installations utilize stone-filled leaching trenches, but galleries, pits and beds have historically been used.
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[See drawing of a typical subsurface sewage disposal system. Then press Back.]
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For a drainage system to function properly it must:
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•1. Provide enough application area. The application area is the amount of surface area of soil provided by the particular drainage system (sides and botttom area of leaching units) where sewage effluent is applied (referred to as "wetted" area). The amount of application area needed for a given house depends on the characteristics of the soils on the property and the daily flows (in gallons) generated from the house. The anticipated flow from a house is usually predicated on the number of bedrooms in the dwelling.
•2. Be surrounded by natural soil conditions that will be able to dissipate and disperse the septic tank effluent discharge without becoming over saturated.
•3. Provide enough capacity to store effluent during periods of unusually heavy use or when rainfall or subsurface flooding reduces the ability of the system to disperse the liquid. Note: Curtain drains / groundwater interceptor drains are sometimes installed upgrade of the drainage system to minimize high groundwater conditions.
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It is important to realize that, once a system has been installed, only one of the above factors can be controlled by the homeowner. The homeowner can control how much water is actually being discharged to the system. Since each system has a set maximum capacity, it behooves the homeowner not to exceed that amount. It should be a goal of the inspection to determine the estimated water usage the existing septic system can handle before it would likely become overloaded and fail.
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If a system starts to experience difficulties, what are some of the common symptoms?
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•1. Plumbing fixtures may exhibit difficulty in releasing its contents (slow draining, bubbling, backups, etc.). This condition may be system related but it could also indicate just a clog in the interior piping or sewer line. The homeowner should have the interior piping checked before proceeding with an investigation of the sewage disposal system. However, on newer systems or retrofits the above symptoms could indicate that the septic tank outlet filter is becoming clogged. In that case tank maintenance is required in order to clean the filter and more than likely pump the tank.
•2. Large volume discharges (such as, washing machines, dishwashers and bathtubs) cause either a backup, as noted above, or, an overflow of sewage above the septic tank or leaching field. This condition is usually at its worst during and / or directly following a heavy rain event.
•3. Foul septic odors in storm drainage piping, catch basins, footing drain piping or curtain drain discharges may indicate that sewage from your or an adjacent property is entering these groundwater systems.
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