You will find the following preliminary tank installation information helpful when making plans for your water storage project. A complete Installation Manual will be forwarded to you upon receipt of a tankage order. Please review this information with your installation contractor and contact Darco for additional information or specific details regarding this process.
DELIVERY OF YOUR FIBERGLASS TANK
1. Deliveries are made only on or very close to public roadways. Do not expect delivery to remote or difficult to access construction sites.
2. Owner or G.C. must inspect tank and sign shipping documents upon delivery.
3. Owner or G.C. is responsible for rigging and offload in a safe and timely manner.
4. Always lift vessels from above rigging to all designated lifting lugs provided.
5. Never wrap chain or steel cable around a tank in order to lift it.
6. Never lift any tank from below with a fork truck or loader bucket.
7. Always use a spreader beam to properly rig and handle large vessels.
8. Improper rigging angles may destroy the lifting lugs causing injury and damage.
9. Always use opposing tag lines to control a tank while in the air.
10. Have your C.O.D. payment ready for our driver prior to offload.
TEMPORARY STORAGE OF VESSELS AT THE JOB SITE
1. Set FRP tanks on a temporary flat bed of soft soil or backfill material.
2. Chock in place with rubber tires and rope down if high winds are likely.
3. Never roll a tank into position over rough or frozen ground.
STANDARD STABLE SOIL SITE REQUIREMENTS
1. Soil bearing must be at least 2000 lbs. / sq. ft. (consult geotechnical engineer).
2. Soil cohesion must be at least 500 lbs. / sq. ft. for vertical side wall integrity.
3. Backslope or bench walls per OSHA 1926.650/P guidelines for stability and excavation safety.
4. If site may be subject to seasonal or unpredictable ground water, do consider:
- Using deadman anchors or a reinforced anchor slab.
- Burying the tank above probable ground water with mounded soil cover.
- Installing a tank bed underdrain ground water collection / discharge pipe.
TANK BEDDING AND BACKFILL MATERIAL REQUIREMENTS
1. Gravel backfill medium must totally bed, surround, and cover the entire vessel.
2. Backfill must be clean, dry, screened and washed aggregate.
3. Individual particles may range from 1/8 to 1/2 inch in size with minimal fines.
4. Aggregate must be structurally sound and weigh at least 95 lbs. / cu. ft.
5. Materials customarily used are natural "pea gravel" or crushed rock "chips".
6. Never use soil, sand, road base, structural fill, or crusher fines as backfill.
BURY DEPTHS FOR DARCO FRP TANK DESIGNS
1. Maximum soil cover depth is 5 feet for tanks with standard wall thickness.
2. Deeper bury depths require additional structure and tank wall thickness.
3. Minimum depth requires burial to "spring line" with mounded cover such that the bottom half of the tank is fully cradled into the excavation for support.
HOLE SIZE AND WORKING CLEARANCE FOR BACKFILL
WARNING: Review OSHA 1926.650/P EXCAVATIONS
1. Allow for 12 inches of bedding material below each vessel.
2. Allow a minimum of 18 inches from the tank to the excavation walls.
3. Allow 18 inches between individual tanks set side by side or end to end.
4. Clearances will need to be increased to accommodate any anchor system.
5. Follow OSHA 1926.650/P open trench excavation safety guidelines when installing tanks.
FULL BURY INSTALLATION PROCEDURE
1. Follow Darco "Fiberglass Tank Installation Manual" provided with your order.
2. Provide 12 inch minimum bedding over soil or anchor slab below tanks.
3. Allow room around and between tanks for hand probing - 18 to 24 inches.
4. Rig and place tank into prepared excavation.
5. When practical, add 10% water ballast to stabilize the tank during backfill. Burial may be done dry (without water).
6. Apply backfill in uniform layers or lifts no more than 12 inches deep.
7. Hand probe under and around the vessel after each lift as illustrated.
8. Backfill with approved gravel until tank is totally covered and no longer visible.
9. Rake surface smooth and apply approved foam insulation board as required in extreme cold climate areas.
10. When insulation is not necessary, overlay the entire exposed gravel surface with geotextile fabric prior to soil cover.
11. Replace soil only as top fill and mound final cover - 5 foot maximum depth.
12. Fill tank with water immediately after backfill is complete to avoid floatation.
13. Secure the manway cover at all times to discourage children and vandals.
14. Review the illustration below depicting the probing process.
- Probe tool is a 3/4 inch metal pipe about 4 to 5 feet long with tee handle and flattened tip to more easily penetrate deep into the gravel backfill.
- No voids or air pockets may exist under tank belly for proper support.
- Probe thoroughly from 4 o'clock to 8 o'clock positions from both sides.
- Probe deeply, but avoid violent tamping, which may disturb the tank.
- IMPORTANT Select backfill gravel must completely cover and encapsulate the tank - below, on all sides, and above - such that the tank is no longer visible.
OPTIONAL ANTI-FLOATATION ANCHOR DETAILS
When FRP tanks are subject to known high ground water conditions created by riparian locations, heavy seasonal run off, natural springs, tidal effects, etc.
1. Follow our installation manual carefully / call Darco for advice in such cases.
2. Form and install deadmen or a reinforced anchor slab below the vessel.
3. Use designated strap locations, anchor hardware, and installation procedure.
VENTING, WEEP TUBES, AND OVERFLOW ASSEMBLIES
All Darco tank systems must be adequately vented to the atmosphere to avoid potentially destructive vacuum or pressure conditions inside the storage vessel.
1. The vent diameter must match or exceed the largest piping in the tank system.
2. A 6 inch internal air space must be maintained at the top of all vessels.
3. Overflow piping must be sized to accommodate highest flow rate anticipated.
4. A weep tube will maintain proper air space if water is delivered by tank truck.
OPTIONAL FLEXIBLE TANK-TO-PIPE CONNECTIONS
It is always a good idea to use some type of flexible coupling between any tank and connecting horizontal pipelines, additional manifolded tanks, or a wet well.
1. Limited tank movement is often caused by minor settling after installation.
2. Pipeline alignment with tank fittings is less critical.
3. Tank shell and fitting strain is kept to a minimum.
4. A full range of axial and radial movement is designed into each elastomeric or stainless steel flexible coupling manufactured or supplied by Darco. Order these optional accessory flex-couplers with your tank if you wish.
TRAFFIC SLABS FOR HEAVY VEHICLES
We recommend that you install tanks under a driveway or building floor only as a last resort when no other suitable alternate location is available.
1. Follow our installation manual carefully and call Darco if you have questions or concerns.
2. Observe the proper backfill depth from tank to slab, based on the tank diameter chart below.
3. Select backfill must be used exclusively - no soil may be replaced between the tank and the bottom of the concrete slab on grade.
4. Traffic slab must be properly reinforced, and of correct thickness and strength.
STANDARD DARCO FIBERGLASS CISTERNS
