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SEPTIC TANK INSTALLATION
144 River Road, Lynden, WA 98264
Phone/Fax 360-354-3912
www.bodesprecast.com
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Proper installation of the tank is absolutely critical
for maintaining the watertightness produced in the plant. Many of the
problems experienced with leakage can be attributed to incorrect
procedures during installation. In addition to damage to the tank,
improper installation techniques could be a safety hazard. |
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Site Conditions
The installation site must be accessible to large, heavy trucks weighing
up to 80,000 pounds. The construction area should be free of trees,
branches, overhead wires, or parts of buildings that could interfere
with the delivery and installation of the septic tank. Most trucks will
need to get within three (3) to eight (8) feet of the excavation to be
unloaded.
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Excavation
Prior to
excavation, all buried utilities should be identified and located.
Excavations should be made with approximately 18 inches of clearance
around the installed tank to allow room for adequate compaction. More
space should be provided, as needed, if work other than installation is
required. Excavations should be sloped to comply with all construction
safety requirements.
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Bedding
Proper use of
bedding material is important to ensure a long service life of an onsite
septic system. Bedding material should be used as necessary to provide a
uniform bearing surface. A good base should ensure that the tank would
not be subjected to adverse settlement. A minimum 4 inches thick
sand or granular bed overlying a firm and
uniform base is
recommended unless otherwise specified. Tanks should not bear on large
boulders or massive rock edges. Sites with silty soils, high water
tables or other “poor”
bearing characteristics
must have specially designed bedding and
bearing surfaces.
Correct compaction of the underlying
soil and bed is critical
to ensure there is no differential settlement. |
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Tank Placement
Prior to placement
in the excavation, the tank’s orientation should be confirmed. Inlet
penetrations should face the residence and the bedding material should
be checked. After placement, check that the tank is level. The slope of
the sewer line and tank should meet local plumbing and building codes.
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Joint Seals
For two-piece
tanks use high quality preformed joint seals. Surfaces should be clean.
Seals shall meet minimum compression and other installation requirements
as prescribed by the seal manufacturer and detailed herein. Tank
sections sealed on site should not be backfilled until the sealant has
settled. Manholes must be properly sealed as well. |
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Backfilling
Backfill should be
placed in uniform, mechanically compacted layers less than 24 inches
thick. This fill should be nearly equally placed around the tank.
Backfill should be free of any large stones (>3 inches diameter) or
other debris. Each layer should
be adequately compacted.
If the water level in the
hole is allowed to rise to a high level, concrete tanks can float.
To prevent floatation during backfilling, fill the tank with water,
place soil on top of the tank or keep water pumped out of the hole until
backfilling is completed.
In extremely cold
weather, it might be necessary for tanks to be insulated before
backfilling. Cold temperatures tend to impede a tank’s natural ability
to digest wastes through anaerobic processes. Once the anaerobic process
begins, cold should have no impact unless the tank is not utilized for
long periods |
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