Installation Manual:
AdvanTex
®
AX20-RT Treatment Units
NIM-ATX-AXRT-1
Rev. 1.0, 1/10
© 2010 Orenco Systems
®
Inc.
7
Step 5: Excavate and Set AX20-RT Unit
Before installing the AX20-RT, consider the depth of the septic
tank and the height of the septic tank outlet. Remember that there
must be a minimum
1
⁄
8
in. per foot slope (10 mm per meter or 1%)
from the outlet of the septic tank to the inlet of the AX20-RT, if
the septic tank uses a gravity discharge. Also, remember that the
AX20-RT lid needs to sit 2 in. (50 mm) above finished grade, to
allow for settling and drainage. Take into account any planned
landscaping that might affect the finished grade of the system.
NOTE:
If you are installing counterbuoyancy flanges, com-
plete step 6a before setting the AX20-RT unit.
Step 5a:
Mark the outline of the excavation. The excavation
needs to extend 18-24 inches beyond all four sides of the unit.
Step 5b:
Excavate the hole for the unit. The AX20-RT unit height
is 72 in. (1830 mm). Make sure that the unit will be set deep
enough to facilitate a minimum slope of
1
⁄
8
in. per foot (10 mm per
meter or 1%) from the septic tank if the septic tank uses a gravity
discharge. Also make sure that the lid will be 2 in. (50 mm) above
final grade after the hole for the unit is excavated and after a com-
pacted bed of aggregate or pea gravel — if necessary — is laid.
Step 5c:
Make sure the bottom of the excavation is stable and
free of debris, especially rocks and other sharp objects.
• If
the base soil is unstable (peat, quicksand, muck, soft or
highly expansive clay, etc.), overexcavate the site depth and
then set a firm, 6-in. (152-mm) compacted base of ½-in.- to
¾-in.-minus (13- to 19-mm) aggregate or pea gravel. In ex-
tremely unstable soil, a concrete layer may be needed to stabi-
lize the bottom of the excavation. If you have any doubt about
the soil’s ability to support the tank,consult a local civil or
structural engineer.
• If
the base soil is rocky or uneven, lay a 4-in. (100 mm) bed
of sand or pea gravel less than
3
⁄
8
in. (10 mm) in diameter, and
compact the material to create an even, smooth surface.
Step 5d:
Use properly sized lifting equipment to attach a chain or
cable to the two lifting brackets on the top of the AX20-RT unit.
Carefully lift and lower the unit into the excavation. When the unit
is set and level in the correct position, remove the chain/cable.
WARNING: Do not allow workers to stand in or near the
excavation while placing the unit!
CAUTION:
Use a lifting device that will not damage the unit
or the lid of the unit.
2 in. (50 mm)
5a
5b
62 in.
(1.57 m)
102 in.
(2.6 m)
5d
5d
Excavate 18-24 in. (457-610 mm) beyond all four sides of
the unit.
Excavate so that the lid sits at 2 in. (50 mm) above final grade.
