Infiltrator Presby Advanced Enviro-Septic Design And Installation Manual page 10

2.0 SYSTEM DESIGN
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If there is no alternative means of disposing of this backwash other than in the system, the system will
need to be "oversized." Calculate the total amount of backwash in gpd, multiply by 2, and add this
amount to the daily design flow when determining the field and septic tank sizing.
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Water purification systems and water softeners require regular routine maintenance; consult and follow
the manufacturer's maintenance recommendations.
Sloping Sites and Sloping Mound Systems
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On sloping sites (>5%) the AES pipe rows and surrounding system sand shall be level.
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Any system sand extension may follow the slope of the site.
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Maximum site slope is 25%.
Row Requirements
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All beds shall have at least 2 rows.
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Maximum row length for any system is 100 ft of pipe.
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Recommended minimum row length is 30 ft of pipe.
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A minimum of two D-box outlets must be used and the field must be vented. Minimum center-to-center
spacing is 1.5 ft for all systems. Spacing may be increased at the discretion of the system designer or as
needed to meet the required SSBA.
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Sewn seam must be oriented in the 12 o'clock position. This correctly orients the Bio-Accelerator
the 6 o'clock position.
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For level beds the AES rows shall be centered in the middle of the system sand bed area (SSBA) and any
system sand extensions (SSE) divided evenly on both sides.
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For sloping beds (>5%): the elevation for the AES rows must be provided on the drawing. All rows shall be
grouped 6 in from the up-slope edge of the SSBA with any system sand extensions placed entirely on the
downslope side. Systems sloping greater than 5% require a 2.5 ft SSE on the downslope side of the bed (3
ft when measured from the pipe).
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Each row must be laid level to within +/- ½ in (total of 1 in) of the specified elevation and shall be parallel
to the contour of the site.
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It is most convenient if row lengths are designed in exact 10 ft increments to accommodate the length of
the AES pipe as manufactured. However, AES pipe lengths can be cut to any length.
System Sand Extensions (SSE)
System sand extensions (SSE) are placed on the down slope side of sloping systems and equally divided on each
side of level systems. The SSE is measured from the tall portion of the system sand bed. In systems sloping more
than 5%, a 2.5 ft minimum SSE is required. The SSE area is a minimum of 6 in deep.
Separation Distances (Horizontal and Vertical)
Horizontal separation distances are measured from the outermost edge of the system sand bed area. Vertical
separation distances are measured from the bottom of the 6 in-deep basal system sand layer to the naturally
occurring suitable or provisionally suitable receiving soil interface.
Design of the AES requires a minimum vertical separation of 12 in. There must be a minimum of 12 in of naturally
occurring suitable or provisionally suitable soil below grade at the location of the system on the site for the AES to
be permitted.
No variances will be issued until the AES system is no longer considered by DHSS to be experimental.
Barrier Materials over System Sand
No barrier materials (hay, straw, tarps, etc.) are to be placed between the system sand and cover material. The
only exception is the placement of the specified fabric to achieve H-20 loading requirements.
© Presby Environmental, Inc., Design & Installation Manual, September 2020 Edition
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fabric in
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