Installation Instructions

Large Volume Tank Installation Instructions (PDF Version - Revised Feb 2008)
5ft Dia. Underground Tank Installation Instructions (PDF Version)
Part 1 | Part 2 | Part 3
FIVE FOOT DIAMETER TANKS Underground Installation Instructions Anchor Kit Assembly and Warranty Information
Installation Instructions for Fiberglass Underground Tanks:
Note: Any deviation from these instructions will void the warranty.
1. Lay backfill bed
USING ONLY specified backfill material, provide a 12“ minimum backfill bed on bottom of hole or concrete slab.
DO NOT place tank directly on concrete slab.
DO NOT use timber, beams, or cradles to support tank.
Allow a minimum of 2’ between tank and hole wall around tank.
2. Backfill under and around tank
It is CRITICAL to ENSURE that all voids and spaces under tank are filled COMPLETELY.
USING ONLY specified backfill material, continue backfilling while filling voids and spaces in uniform layers not greater than 12“ deep.
AVOID excessive side-loading of manway with gravel by filling in UNIFORM 12" layers
3. Backfill to top
USING ONLY specified backfill material, continue backfilling in uniform layers not greater than 12“ deep, TO WITHIN 12” OF THE SURFACE.
WARRANTY REQUIRES THAT NO VEHICLES OR HEAVY LOADS BE ALLOWED OVER TANK AT ANY TIME. Contact us for special order tanks that will accommodate traffic or extreme water conditions and any other adverse situations the tank may be subjected to.

Installation Instructions

The following materials are specified for backfilling underground fiberglass tanks. If other materials are used, warranty will be void.
Pea Gravel, 1/8“ to 3/4” diameter
A naturally rounded aggregate, clean and free flowing, with particle size not less than 1/8“ and not more than 3/4” diameter, with NO MORE THAN 10% fines.
Stone or Gravel Crushings, 1/8“ to 3/4” diameter
Crushed stone or gravel, clean and free flowing, with angular particle size not less than 1/8“ and not more 3/4” diameter, clean and free flowing, with NO MORE THAN 10% fines.

Important Notes:

The object of backfilling is to form a uniform, homogeneous envelope of firm backfill all around the tank. Backfill material must not contain foreign materials such as rocks, brick, wood, native soil, etc.
SHARP OBJECTS MUST NOT COME IN CONTACT WITH THE TANK. Remove any supports used for installation of piping prior to backfilling.
It is recommended that a flexible or plumber’s joint (known as 4“ MJ or Fernco) be installed to compensate for ground movement.
If liquid is to be present in the tank during installation, LIQUID LEVEL MUST NOT EXCEED THE LEVEL OF THE SURROUNDING BACKFILL BY MORE THAN 24“.
To avoid floating during spring thaw or high water table conditions, use tie downs or leave the tank approximately 1/3 full over the winter months. This weight will help keep the tank in place. If sewage or water freezes in the tank when it is only 1/3 full, this will not harm the tank as there is enough expansion room. Do not allow liquid to freeze with more than 1/3 full or warranty will be void.
No vehicle traffic is allowed over regular duty tanks. Call for details on heavy duty tanks.
Gravel Requirements (Cubic Yards req'd per Burial Depth of Cover Above Tanks):