How to Read a Tank Specification Sheet
How to Read a Tank Specification Sheet
Every tank comes with a specification sheet listing dimensions, ratings, materials, and certifications. If you know how to read it, the spec sheet tells you everything you need to know about whether a tank fits your application. If you don't, you might miss a critical rating or dimension that makes the difference between a successful installation and an expensive mistake.
Understanding the technical fundamentals behind polyethylene tank construction, ratings, and specifications helps you make better purchasing decisions and avoid costly mistakes. This guide explains what the numbers actually mean and how they affect real-world performance.
Dimensions: What the Numbers Mean
Tank dimensions are listed as diameter × height for vertical tanks, or length × width × height for rectangular/doorway tanks. Diameter is the outside dimension — the footprint on your foundation. Height includes the dome top but not fittings or vents that protrude above it. For planning purposes, add 6-12 inches to the listed height for fittings and vent clearance. Clearance from walls should be at least 12 inches minimum, 24 inches preferred, for inspection and maintenance access.
Capacity and Working Volume
The listed gallon capacity is the total volume to the top of the tank. Working volume — the practical amount you can store — is typically 90-95% of listed capacity. You need air space above the liquid for expansion, venting, and to prevent overfilling from splashing during fill operations. For heated liquids, additional expansion volume is needed. A good rule: your maximum fill level should leave at least 5% air space.
Weight: Empty and Full
The spec sheet lists empty weight (the tank itself) and may list full weight at rated SG. If only empty weight is listed, calculate full weight: Full Weight = Empty Weight + (Capacity × 8.34 × SG). This number determines your foundation requirements, delivery logistics, and whether your installation location can support the load. A 2,500-gallon tank of water weighs over 20,000 pounds — that is 10 tons on a footprint about 7 feet in diameter.
Certifications and Compliance
Look for: FDA 21 CFR 177.1520 (potable water/food contact), IAPMO (septic tanks), NSF/ANSI 61 (drinking water system components), ASTM D1998 (standard specification for poly tanks). These certifications are not interchangeable — each covers a different requirement. An FDA-approved tank is not automatically IAPMO-certified, and vice versa. Match the certifications to your application requirements.
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Key Takeaways
- Always verify your liquid's specific gravity before selecting a tank — exceeding the rated SG is the most common cause of premature tank failure
- Polyethylene tanks are chemically resistant to most substances but NOT all — always check the compatibility chart for your specific chemical
- Proper installation is more important than the tank itself — a premium tank on a bad foundation will fail before a basic tank on a good foundation
- UV stabilizers extend life but don't eliminate UV damage — shade structures are cheap insurance for tanks in full-sun locations
- Temperature matters — polyethylene softens above 120°F and becomes brittle below -40°F. Plan for your climate extremes.
Questions about tank specifications? Call (866) 418-1777 — we speak fluent tank and can translate technical specs into practical guidance for your application.
Understanding Polyethylene Tank Construction
Every polyethylene tank in our catalog is manufactured through rotational molding — a process that creates a seamless, one-piece structure from powdered HDPE resin. The mold rotates on two axes simultaneously while heated, distributing molten resin evenly across all interior surfaces. The result is a tank with no seams, no weld lines, and no potential leak points. This seamless construction is the primary advantage of rotomolded tanks over welded or fabricated alternatives — joints are where tanks fail, and rotomolded tanks have no joints.
The resin itself is not generic plastic. It is a specially formulated compound that includes UV stabilizers (to prevent sun degradation), antioxidants (to prevent thermal degradation during processing and service), and pigments. For potable water applications, the resin meets FDA 21 CFR 177.1520 requirements for food-contact materials. These additives are compounded directly into the resin — not applied as surface coatings — which means the protection extends through the full wall thickness and lasts the life of the tank.
Why Buy from OneSource Plastics?
OneSource Plastics is not just another tank reseller. We are a specialized industrial tank dealer with deep product knowledge, competitive pricing from direct manufacturer relationships, and a commitment to helping you select the right tank for your specific application. Our team handles tank inquiries every day — we know the product lines, the specifications, the common pitfalls, and the solutions.
When you call us, you talk to someone who knows the difference between a 1.5 SG and a 1.9 SG tank, who can explain why a cone bottom is worth the extra cost for your mixing application, and who can tell you exactly what foundation your 2,500-gallon tank needs on your specific soil type. We don't just process orders — we solve liquid storage problems.
Every tank we sell ships with the full manufacturer warranty. We handle freight logistics to all 50 states, and we can coordinate delivery equipment for sites with challenging access. If something goes wrong — a shipping damage claim, a warranty issue, a specification question — we handle it directly. One call to (866) 418-1777 connects you to a real person who can actually help.
Shipping and Delivery Information
We ship polyethylene tanks to all 50 states via the most cost-effective method for each order size. Small tanks (under 150 lbs) ship via UPS or FedEx ground — typically 3-7 business days. Medium tanks ship via LTL freight on pallets — schedule a delivery appointment and request liftgate service if you don't have a loading dock. Large tanks ship via flatbed — you'll need a forklift or equipment for unloading.
Freight cost for polyethylene tanks is driven by size (cubic feet), not weight. A 1,000-gallon tank is physically large — over 5 feet in diameter and 6 feet tall — and takes significant truck space even though it weighs only 100-200 pounds empty. We quote freight individually for each order because rates vary significantly by destination, carrier, and accessorial services like liftgate and residential delivery.
For the most accurate freight quote, call us with your zip code and the products you're considering. We ship daily and know which carriers provide the best rates and service to each region of the country.
Example: Reading a Real Spec Sheet
Below is a filled-out tank specification sheet based on a real product — the Norwesco 500 Gallon IAPMO-Certified Septic Tank (part number 41320). This is exactly what you'll see when you pull the PDF spec sheet from a manufacturer's catalog. Every field is annotated so you can see what to look for.
| Manufacturer Part Number | 41320 ← Always cross-reference this to the PDF you get |
| Capacity (gallons) | 500 ← Nominal — actual fill at rated SG may differ |
| Diameter (in) | 67 |
| Overall Height (in) | 47 ← Check this against your burial-depth requirement |
| Material | HDPE (linear polyethylene) |
| Specific Gravity Rating | 1.0 ← Water-rated. For denser liquids order a 1.5 or 1.9 tank |
| Color | Yellow ← Legacy septic pump-tank color |
| Certifications | IAPMO, CSA, FDA ← Verify jurisdiction before permit submittal |
| Warranty | 3-year full replacement (Norwesco 2024 catalog) |
| Shipping Weight | 115 lb |
| Fittings/Manway | 20" domed manway, 4" inlet/outlet bulkheads |
How to Fill One Out for Your Project
- Start with your MPN. Copy it exactly from the OEM catalog (no reseller codes). This is how the manufacturer tracks warranty.
- Confirm capacity vs. specific gravity. A 500-gallon tank rated 1.0 will only hold 260 gallons of liquid at 1.9 SG. Always cross-check your fluid density.
- Measure your space against diameter × height. Add 6 inches clearance on all sides for fitting access and venting.
- Verify certifications for your jurisdiction. Septic requires IAPMO in most states; FDA contact for potable water; CSA for Canadian projects.
- Record warranty terms. Most rotomold warranties require original purchase receipt — keep the order confirmation.
- Document fitting sizes before ordering accessories. Bulkhead fittings come in sizes 3/4" through 4" — match exactly.
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