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2500 Holding Tank Installation
1. Excavation
A. Excavate to a depth that will provide a minimum of 6" and a maximum of 24" of cover over the top of the tank.
B. Allow 18" to 24" on both sides and both ends of the tank.
C. Bed the tank in well - compacted sand - 6" minimum in soil terrain, 12" minimum in rock terrain.
2. Connections to Tank
A. Install fittings in any location required for holding tank use.
B. Contact factory for approval if multiple fittings are installed in close proximity.
C. Tank must be vented.
D. For water-tight seal, lid should be sealed with silicone or urethane caulking. Re-use stainless steel screws supplied with lid to re-attach lid to tank.
3. Manhole Extension
A. Install manhole extension before you backfill.
B. Norwesco manhole extensions are supplied with gaskets and screws. Re-use the stainless steel screws to attach the lid at the top of the manhole extension.
4. Backfilling Exterior
A. Backfill with 12" layers and compact each layer. Always compact ends first.
B. Each of the interior support cones must be filled and compacted in 6" layers; the bottom half of the cones are tapered and must have the soil compacted to provide structural support. See diagram.
C. Maximum backfill over the top of the tank is 24". Mound soil over the top to provide positive drainage.
5. Backfill Materials
A. The preferred material for backfilling, surrounding and covering the tank is a sand and gravel mixture - 100% smaller than 1/2" and approximately 50% smaller than 1/4". Native soil can be used if this mixture is not available.
B. All fill must be free of any wood, masonry debris, silt or clay. Sharp object must not come in contact with the wall of the tank.
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