2.0 SYSTEM DESIGN
© Presby Environmental, Inc., Design & Installation Manual, July 2020 Edition
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Illustrations of Multi-Level™ EQ Combination Distribution Systems:
Individual D-box Distribution
Individual D-box distribution is a configuration where every EF unit is fed individually from a D-box outlet.
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Flow equalizers must be used in the D-box outlets feeding the EF units.
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Each EF unit requires a modified inlet “Tee” baffle.
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EF units may be contained in a single or multiple beds.
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EF units may be arranged at a single elevation, different elevations, or on a slope.
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The D-box outlet invert will be at or above the elevation of the highest EF unit’s inlet invert.
Multiple Bed Distribution
Multiple bed distribution incorporates two or more beds (single level or Multi-Level™), each bed with EQ flow, EQ
combination, or individual D-box distribution. Multiple beds may consist of different size beds, as long as the D-
box outlet ratio matches the ratio of EF units within the beds. For instance: 3 beds with 3 EF units in the first bed,
2 EF units in the second bed and one unit in the third bed would be fed from a D-box by 3 manifolded outlets, 2
manifolded outlets and a single D-box outlet, respectively. Multiple beds may be oriented along the contour of the
site, along the slope of the site or at different elevations.
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In multiple bed distribution, a single bed may consist of as little as a single EF unit.
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Multi-Level™ systems may be used in multiple bed configurations.
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The D-box outlet invert will be at or above the elevation of the highest EF unit’s inlet invert.
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Test pit/perc tests should indicate the soils in each bed location, allowing the ability to size each
location according to soil type.
Illustration of End-to-End Multiple Beds:
Illustration of Side-to-Side Multiple Beds: