A, B, C —
and the rebottle rung.
Every incoming tank is graded on four axes: cage integrity, valve condition, residue origin, and HDPE translucency. The worst axis wins. Here's exactly how we translate that to a letter — and what you should buy for your job.
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| Grade | Cage | Valve | Previous contents | HDPE appearance |
|---|---|---|---|---|
| A · Food | Straight, no rust | OEM, sealed | Labeled food-grade (syrup, juice, cider, water) | Clear, glass-like |
| B · Industrial | Straight, minor cosmetic rust okay | Any working 2″ ball | Known industrial: soaps, glycols, detergents, fertilizers | Tinted or slight haze okay |
| C · Raw | Bent okay if structurally sound | Functional, may be third-party | Known and non-toxic | Haze/residue visible |
| Rebottled | Original cage straightened | New OEM | N/A — new inner bottle | Brand new virgin HDPE |
When to choose Grade A
Food contact, beverage production, maple syrup, cider, honey, water bottling, brewery use. Any time you'd be uncomfortable explaining the tank's prior life to a health inspector.
When to choose Grade B
Soap making, biodiesel production, detergent blending, fertilizer mixing, fuel transfer, glycol storage, most agricultural chemical handling. Best value in the line.
When to choose Grade C
Rainwater, ballast, flood barriers, equipment washdown, irrigation, landscaping, non-potable holding. You'll clean it yourself or it doesn't matter.
Need advice?
Email us what you plan to store and we'll tell you the smallest grade that's safe for the job — not just the biggest one we could sell you.
Email the yard →Quantitative thresholds, tank by tank.
We measure before we letter. Here are the numeric cutoffs our foreman uses at the intake bench — same rubric on a Monday morning as on a Friday afternoon.
| Axis | Grade A ceiling | Grade B ceiling | Grade C ceiling | Reject if |
|---|---|---|---|---|
| Cage deflection (worst strut) | ≤ 0.10 in | ≤ 0.25 in | ≤ 0.50 in | > 0.50 in or weld crack |
| Cage rust coverage | < 2% surface | < 10% surface | < 25% surface | Through-wall penetration |
| HDPE wall thickness (min) | ≥ 1.9 mm | ≥ 1.7 mm | ≥ 1.5 mm | < 1.5 mm at any measured point |
| HDPE translucency (Delta-E) | < 3 from new | < 12 from new | < 25 from new | Visible interior residue after wash |
| Cumulative UV exposure | < 18 months outdoor | < 36 months outdoor | < 60 months outdoor | > 60 months unsheltered |
| Valve condition | OEM, sealed, new gasket | OEM working, new gasket | Aftermarket accepted | Leak at any test pressure |
| Pallet condition | No splits, no rot | Minor splits okay | Functional 4-way access | Broken deck board or stringer |
| Residue origin | Labeled food-grade only | Named industrial, non-toxic | Named non-hazardous | Unknown or hazmat |
Worst-axis rule: a tank's grade is set by whichever row scores lowest. A perfect cage with a clouded HDPE bottle is still a Grade C. This is why we publish the rubric — it's the only way a customer can spot-check us.
How a tank moves through the rubric.
Walk-around, tap the cage, spin the valve, smell the interior. Photograph the UN plate. Tag with a paper slip carrying a fresh six-digit ledger ID.
Ultrasonic wall-thickness gauge at twelve points. Calipers on the worst cage strut. Rust-coverage estimate against a printed reference card.
For labeled tanks, a paperwork check and a sniff. For any tank where label and contents disagree, a mass-spec screen before the tank enters the wash queue.
Triple rinse at 180 °F, sanitizer where applicable. Translucency re-checked against a Delta-E card after the bottle is clean and dry.
Required for Grade A and Rebottled units; spot-check for Grade B. Hydrostatic hold at 100 kPa, pass/fail stamped on the UN plate.
Grade assigned, photos uploaded, outbound category set (retail, pellet, or awaiting sale). The paper tag is archived with the intake form.
When to pay extra for rebottled.
Rebottling runs a modest premium over a top Grade A. It's worth it in a handful of specific cases and overkill in most others. Here's how we counsel buyers.
Rebottle is worth it when
- You're bottling for retail sale of a consumable (cider, syrup, cold-brew concentrate, kombucha).
- You need to present a UN31A stamp dated within the last 12 months to a customer or inspector.
- Your product is pigmented or high-solids and even trace interior discoloration would be visually disqualifying.
- Your liability insurance requires new inner packaging for every batch.
- You're running a sanitary CIP cycle and want a glass-clear interior for visual confirmation.
Grade A is sufficient when
- You're producing non-retail food-grade liquids for your own operations (brewery wort, in-house syrup, water softener brine).
- You can demonstrate your own triple-rinse and sanitize protocol on intake.
- Your product will be pasteurized or heat-processed downstream.
- You're storing potable water for municipal backup or agricultural frost protection.
- You need the certification for a service that accepts the current UN31A recert date.
Complaints, and what we do about them.
Our grading has been wrong before. Three tanks in the last twenty-four months, to be exact. Here's what happened and what changed.
A cidery caught a slight soapy finish on the first fill. We exchanged the tank same-week, ran the original back through a four-rinse cycle, and re-graded it to B. Root cause: our sanitizer dilution ratio drifted by 14% across an eight-hour shift. We now check the doser twice per shift and log the reading.
A soap-maker reported a weep at the threads on day six. We replaced the valve assembly on-site, refunded the tank, and switched our default Grade B gasket from generic EPDM to a supplier we'd been using only on Grade A. Incremental cost: a rounding-error addition per tank.
A customer stacked two Grade C units outdoors in 14 °F weather. The bottom pallet cracked after ten days. We replaced both pallets and added a note to our grading sheet: outdoor winter storage means we sell only steel-pallet Grade Cs if we sell them at all.