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SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
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SEPTIC INSPECTION & TEST GUIDE
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SEPTIC SYSTEMS, HOME BUYERS GUIDE to
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SOAKAWAY BED FAILURE DIAGNOSIS
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
TRAPS on PLUMBING FIXTURES
TREATMENTS & CHEMICALS, SEPTIC
VIDEO GUIDES: Septic Videos
WATER CONSERVATION MEASURES
WATER SOFTENERS & CONDITIONERS
WATER SUPPLY & DRAIN PIPING
WATER, WELLS, WATER TANKS: TESTING GUIDE
WASHING MACHINES & SEPTIC SYSTEMS
WASTEWATER TREATMENT BASICS
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Specifications for drywells or seepage pits or soakpits:
This document discusses and describes design specifications for seepage pits and drywells. We describe sepage pit size, area requirements, depth, and other construction requirements if you plan to use a seepage pit for roof or site drainage, to receive graywater or to receive septic effluent.
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(i) If soil and site conditions are adequate for absorption trenches, seepage pits shall not be used.
(ii) A minimum three foot vertical separation must exist between the bottom of any pit and the high groundwater level, bedrock, or other impervious layer.
(i) The required "effective seepage pit area" is obtained from Tables 6 and 7 which are shown below.
(ii) No allowance for infiltration area is made for the bottom area of a pit or the surface area of impervious soil layers (percolation rate slower than 60 minutes/inch).
(iii) The effective diameter of a seepage pit includes the diameter of the lining plus the added diameter provided by the annular ring of aggregate. Any area surrounding the liner with rock smaller than 2 1/2 inches in size shall not be included as part of the effective diameter.
(iv) Effective seepage pit depth is measured from the invert of the seepage pit inlet to the floor of the pit, with the thickness of impervious layers deducted.This sketch (from New York's Wastewater Regulations) shows the recommended site clearances between seepage pit (used to receive septic tank effluent in this case) and other building and site features.
A more detailed list of site clearances between all site features and all types of septic system components is listed at "More Reading" just below.
Notice that absorption pits like this one not only need to be at a sufficient distance from the building, from wells, from property lines, but also if multiple absorption pits are installed, if you expect each pit to dispose of the graywater or effluent sent to it, they should be adequately separated from one another.
The table given above for historical purposes, shows and older copy of the required soil absorption area for seepage pits as a function of soil percolation rate and anticipated daily wastewater flow in gallons. A current seepage pit sizing table is given just below.
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TABLE 6 - SEEPAGE PITS - REQUIRED ABSORPTIVE AREA (IN SQUARE FEET) FOR HOUSEHOLD SYSTEMS
Given in more detail here:
The table below shows the size of seepage pit necessary in order to provide the required soil absorption area for seepage pits. First use the preceding table to determine the necessary seepage pit absorption area, then use this table (below) to determine the necessary seepage pit size to provide that absorption area.
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TABLE 7 - SEEPAGE PITS (CYLINDRICAL) - DIMENSIONS FOR REQUIRED ABSORPTIVE AREA (IN SQUARE FEET)
Older copy for historical reasons:
Continue reading at DRYWELL / SEEPAGE PIT CONSTRUCTION DETAILS or select a topic from the More Reading links shown below.
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Questions & answers & design specifications: how to design and build a drywell or seepage pit for graywater or septic effluent disposal
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