© Presby Environmental, Inc., Maine Design & Installation Manual, June 2019 Edition -15-
21.0 D-box Distribution (Single Level)
a) All rows in this configuration must be the same length.
b) Flow equalizers must be used in the D-box.
c) Use a Manifold to connect the ends of all rows. Manifold to be sloped toward AES or ES pipes.
d) Maximum row length is 100 ft.
e) Place the D-box on level, firmly compacted soil.
f) All rows must be laid level end-to-end.
g) A 2 in. min. drop is required between the D-box outlets and the AES or ES pipe inlets.
h) System Sand Extension (if required) placed entirely on downhill side of bed (as shown).
i) D-box systems are not recommended for use in Multi-Level™ beds.
Illustrations for D-box (Parallel) Distribution:
22.0 Multiple Bed Distribution
Multiple Bed distribution incorporates two or more beds (Single Level or Multi-Level™), each bed with Basic Serial,
Combination Serial, or D-box distribution, and each receiving an equal amount of effluent from a D-box. Multiple beds
may be oriented along the contour of the site or along the slope of the site.
a) Each bed must have the same minimum linear feet of pipe. The minimum linear feet of pipe per bed is
determined by dividing the total linear feet of pipe required in the system by the number of beds.
b) Rows within a bed may vary in length to accommodate site constraints, except with D-box configuration
which requires all rows to be the same length.
c) End-to-End configurations are preferred to Side-to-Side configurations.
d) In Side-to-Side configuration, one bed is placed beside another or one bed is place down slope of
another. Bed separation distance is measured from pipe-to-pipe.
e) Multi-Level™ may be used in multiple bed systems.
Illustration of End-to-End Multiple Beds:
Illustration of Side-to-Side Multiple Beds:
23.0 Elevated Bed Systems (Mounds)
Elevated beds are designed for sites with soil, depth to groundwater or restrictive feature constraints that do not allow
for In-Ground Bed Systems. An elevated bed system is a soil absorption field with any part of the field above original
grade. Elevated bed systems require 3 ft. fill extensions on each side (measured from the pipe), and 5 ft. on the
downhill side of beds sloping greater than 10%, after which side-slope tapering is to be a maximum of 4 horizontal
feet for each 1 foot of vertical drop until it meets existing grade.
