The biggest price differences between tanks generally are caused by the tank provider not including these few items.
This could explain the cost difference between the tank quotes you are comparing.
1. Site-specific PE wet-stamped engineering drawings. Your site-specific location for the tank can and most likely will change the tank dimensions, usable capacity, and loading requirements. Each site is unique and has its own seismic, wind, snow load, and soil conditions, which can and may affect what you can install at your site. If your provider does not run a calculation before providing you with a price, they are underbidding.
2. Know your capacity requirements and what code you are required to meet.
3. Site-specific PE wet-stamped foundation design- This generally requires a recent, accurate soil report provided by the customer to provide a site-specific foundation design and anchoring detail. Do not accept a non-site-specific, simplistic example drawing as approved. It is not engineered for your site. If you mistake the simple, non-site-specific drawing for an approved, site-specific drawing without a wet stamp, you may have to replace it when reviewed by the AHJ.
4. Tank Insulation and Immersion Heat (remember, even if provided by the tank supplier, installation of immersion heat and electrical are generally not included)
5. Tank liner meeting NFPA22 table or NSF61 required certification. Minimum 25 mil thickness, welded and tested to AWWAD130. A geotextile or preliner must be included inside the tank, behind the liner, on the walls, and floor.
| a. | Weight | ATSM D751 25 oz./ sq yard (840 g/m² - 33 g/m²) |
| b. | Thicknes | ATSM D751 0.027 in. - 0.003 in |
| c. | Breaking Strength | ATSM D751 Warp 175 lb. (778 N)average/ Fill Grab Method A 175 lb. (778 N) average |
| d. | Elongation at Yeild % | 20% |
| e. | Tear Strength | ATSM D751 War 35 lb. (155 N) Average/ Fill Tongue 35 lb. (155 N) average |
| f. | Adhesion of coating to fabric | ATSM D751 20 lb.s/ 2in. (89 N/5 cm) |
| g. | Dimensional Stability | ATSM 1294 2.0% |
| h. | Puncture Strength (Rod) | ATSM D4833 100 lb.(445 N) |
| i. | Cold Crack/Bend 1" | ATSM D2136 -30° / -34° |
| j. | Bursting Strength (Ball) | ATSM D751 220 lb. (979 N) |
| k. | Abrasion resistance | ATSM D3389 Wheel H-18 Taber Test 2000 cycles/ weight 35 oz (1000 g/wheel) |
| l. | Wicking Test | ATSM D751 <0.5 in. (12.7 mm) |
| m. | Blocking Resistance | ATSM D751 Rating of 1. Maximum @70 C 6 hrs |
| n. | Minimum Overlap Seam width (excluding encapsulated edge) | ATSM D751 1-5 in. |
| o. | Bonded Seam strength (Grab), 2" (51 mm) wide specimen | ATSM D751 Method A 20 lbs./ 2 in. (89 N/ 5 cm.) |
| p. | If potable water specification is required (Raw Material) | NSF 61 Tested and Certified |
6. Coatings- make sure to compare corrosion-resistant coatings. Galvanized tanks come in different thicknesses, which determine their corrosion lifespan. G90- is the lowest quality and lowest life span. Your coating should be a minimum of G115 for the walls and G140 for the roof (as the roof will take the brunt of the atmospheric conditions.
G115 offers approximately 28% more corrosion resistance than G90 (1.15 oz/ft² is 28% greater than 0.90 oz/ft²).
G140 offers approximately 56% more corrosion resistance than G90 (1.40 oz/ft² is 56% greater than 0.90 oz/ft²).
G140 offers approximately 22% more corrosion resistance than G115 (1.40 oz/ft² is 22% greater than 1.15 oz/ft²).
7. The correct size and amount of nozzles required for the application, including anti-vortex assembly required on fire outlets. There should be a minimum of a fill/inlet, overflow, outlet, and drain. Anti-vortex assembly, couplers for temperature switch, and two-level alarms are for NFPA 22. PVC fittings are not compliant with NFPA 22 or AWWA.
8. Temperature switch- required for all NFPA22 tanks regardless of location or temperature in that area
9. High Low Level float alarm- required by NFPA22 for all tanks used for fire protection (including the nozzles or couplers installed on the tank for those components). These are third-party parts, and most tank suppliers do not provide installation of these components.
10. Anchoring- All corrugated tanks require anchoring unless they have a full steel floor and are designed to meet self-anchoring engineering design standards. Anchor bolts and installation need to be included and provided
11. Vents- You must have a minimum of one mushroom roof vent or gooseneck roof vent designed per code with a minimum of 24″ screen area
12. Frost-free roof Vents- This is required for snow-loaded areas
13. Installation- make sure your tank includes onsite installation and freight with licensed, manufacturer-certified/qualified tank erectors. If the price seems low its because something is missing.
14. Manway access- It is required to have a minimum of 2 manway access openings. This is for safe access into the tank for repairs and maintenance, as well as during erection. OSHA has requirements for these openings. Full Access: means the manway must be accessible for a person to enter and exit at any time. An OSHA side wall or side shell manway is a minimum of 24″ and is a full access, non-obstructed opening with a bolt-on lid. It is located at the bottom or first ring of the tank, allowing a person to enter and exit from inside the tank. Many tank suppliers do not include a full, unobstructed manway. They provide a smaller wall panel with bolts, attached to the corrugated wall, inaccessible due to the liner being behind the wall and obstructing entry. It is common to provide either two side wall/side shell manways, or one side shell manway and one roof manway, or a visual access port. The roof manway can be used to enter and exit the tank, but usually only used for visually checking the level.
15. Lightning Protection: This is a requirement by NFPA22 for fire protection tanks. This is generally excluded from most scopes, but is a requirement for the customer to install on the tank.