3.0 INSTALLATION
© Presby Environmental, Inc., Design & Installation Manual, July 2020 Edition
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Horizontal Sanitary Tee (not supplied)
Attached to the 4-in sewer line from the septic tank or D-box is a horizontal 4-in sanitary tee, which is used to
create an inlet baffle inside the FDU. The sanitary tee is not supplied by PEI. The downspout portion of this baffle
must be sized to locate the bottom of the baffle 2.5 in (+/- ½”) from the bottom of the FDU. This baffle system is
only required in the first EF unit. When connected in series, subsequent units utilize equalized flow distribution (EQ
distribution) through the bottom connection, so a tee is not required.
Illustration of
Horizontal
Sanitary Tee:
Sanitary Tee
Enlarged
:
Distribution Box Installation
It is essential that the D-box remain level after installation in order to ensure even distribution to all rows within
the system. To prevent movement, the D-box shall be set on a layer of level compacted soil, sand, pea gravel base
or a concrete footing. Take care when backfilling that the D-box remains level.
Distribution Box (D-box) Manifold for Splitting Uneven Flows
Divide flows to uneven sections or multiple beds by manifolding D-box outlets
such that each outlet feeds a single EF unit. Example: Two sections, one with 2
EF units and the other with 3 EF units. Manifold 2 D-box outlets to one section
and 3 outlets to the other section. This configuration will divide flows
appropriately. Flow equalizers are required in all D-box outlets which split
effluent flows.
Level Row Tolerances
Use a laser level or transit to install the EF unit level. Variations beyond 1/2 in (± ¼ in) for the FDU and variations
beyond 1 in (± ½ in) for the treatment fins may affect system performance and are not acceptable.
Installing Stackable FDU (Riser) as needed
Some installations will have more material cover than traditional systems which may place access to the top of the
FDU cover more than 12 in below grade. PEI offers an optional extension kit called a stackable FDU that is placed
on top of the lower FDU. The cover is then attached to the top of the stackable FDU. Use the following procedure
when an FDU extension is required once the bottom FDU, treatment fins, and
system sand are installed:
a)
Join two stackable FDU halves with the supplied stainless-steel screws.
b)
Remove cover from bottom FDU.
c)
Place and secure stackable FDU on top of the lower FDU (in place of the
cover) making sure the alignment tabs on the stackable FDU are inside
the lower FDU. Screw the upper FDU to the lower FDU with the supplied
stainless-steel screws.
d)
Place and secure cover on stackable FDU.
e)
The 4-in diameter cutout in the stackable
FDU can be used as an alternate location
for the vent.
f)
Install design-required fill sand and topsoil
around the stackable FDU.
Sweep
Flow
Equalizer