Chemical Storage Tank Approved Equal Comparison
Poly Processing vs. Snyder Industries vs. Assmann, for sodium hypochlorite storage — including a real, documented resin disagreement most substitution requests never surface. LibertyCES presents both positions; the engineer of record makes the call.
30+ years spec experience. Send James your basis-of-design tank spec and proposed alternate — get the real material comparison, not a sales pitch.
Request a Spec Review →Chemical storage tank specs for sodium hypochlorite are one of the clearest cases where a substitution request needs more than a size and material match — it needs the actual resin-family reasoning, because the three manufacturers with the most documented data on this exact chemical genuinely disagree on the right resin. This page presents that disagreement directly, alongside the requirements all three vendors do agree on.
Poly Processing vs. Snyder Industries vs. Assmann — Sodium Hypochlorite Storage
| Requirement | Basis of Design — Poly Processing | Alternate — Snyder Industries | Alternate — Assmann | Same / Different | Notes |
|---|---|---|---|---|---|
| Resin family for sodium hypochlorite | Poly Processing — cross-linked polyethylene (XLPE) with OR-1000™ antioxidant protection on the flange face | Snyder Industries — HDLPE (high-density linear PE), not XLPE | Assmann — XLPE or LLDPE, min. 1.9 specific gravity | Genuinely unsettled | This is a real, documented manufacturer disagreement, not a settled industry consensus. Snyder's own accelerated-aging test data (6-month exposure to 16.5% NaOCl at -40°F) showed HDLPE retaining 400 ft-lb of Izod impact strength vs. XLPE at only 160 ft-lb, and Snyder cites a third-party guide stating XLPE is "not as good as HDPE" for this chemical. Poly Processing and Assmann independently favor XLPE/LLDPE. Present both positions to the engineer of record — do not pick a side in a submittal. |
| Full-drain outlet design | Poly Processing IMFO® (Integrally Molded Flanged Outlet) — one-piece molded flange, same material as the tank, full drainage below the knuckle radius, no tank entry needed | Snyder — titanium SUMO® fitting (2"-6") for periodic flushing, recommended every 6 months | Assmann — titanium fittings to eliminate cross-sectional metal exposure (general guidance, not a named drain-fitting product line) | Same intent, different mechanism | All three vendors solve the same real problem — salt buildup and crystallization at the tank outlet — but with different hardware. IMFO is molded into the tank; SUMO is a bolt-on titanium fitting. Verify piping-connection compatibility with the specified fitting before treating either as a drop-in match for the other. |
| Vent sizing | Not explicitly quantified in Poly Processing's captured tank-offerings literature | Not explicitly quantified in Snyder's captured sodium hypochlorite bulletin | Assmann explicitly states vent sized at 2x the largest inlet fitting — "under-venting is one of the most common causes of tank failure" | Unverified for two of three | Assmann's explicit 2x-inlet vent-sizing rule is real and worth applying as a baseline check regardless of which resin/vendor is ultimately specified — but confirm the exact vent size against the selected vendor's own current tank drawing before finalizing a submittal. |
| Specific gravity rating | Built for 1.9 SG service across Poly Processing's sodium hypochlorite-relevant tank lines | Snyder tanks built to ASTM D1998, 1.9 specific gravity across its named hypochlorite product line | Assmann — minimum 1.9 specific gravity stated explicitly | Same | All three vendors converge on the same 1.9 SG minimum for sodium hypochlorite service — a genuinely matched requirement across the whole comparison, unlike the resin question above. |
| Governing standard | Rotationally molded polyethylene tank construction (Poly Processing's own literature does not cite ASTM D1998 by name in the captured tank-offerings page, though it is the standard rotomolded-PE tanks are built to) | Snyder — explicitly built to ASTM D1998 | Assmann — rotationally molded, uniform wall thickness stated as reducing UV penetration | Consistent, confirm by name | ASTM D1998 (Standard Specification for Polyethylene Upright Storage Tanks) is the real governing standard for this tank class — confirm it is cited by name on whichever vendor's current tank drawing is submitted, since not every capture in this comparison names it explicitly. |
| UV / heat exposure handling | OR-1000™ antioxidant protection (flange-face specific) | Opaque-white Resin #880059 — reflects UV/heat rather than absorbing it, avoiding the tradeoff of black-pigmented tanks (which block UV but absorb heat) | Uniform wall thickness reduces UV penetration (general guidance, no named resin/color system) | Different mechanisms, same goal | Snyder's reflective-resin approach is a distinct, real engineering solution from Poly Processing's antioxidant-additive approach — both address UV/heat degradation, neither is simply a copy of the other. |
Sources: Poly Processing tank-offerings and chemical-storage literature; Snyder Industries Sodium Hypochlorite Storage technical bulletin (real accelerated-aging test data, printed 9/2019); Assmann Corporation sodium hypochlorite storage application page and spec sheet.
FRP Tank Resin Selection — a Related but Distinct Question
This comparison covers rotationally molded polyethylene tanks (XLPE vs. HDLPE). A separate, related decision — isophthalic polyester vs. vinyl ester resin in fiberglass-reinforced plastic (FRP) tanks for sodium hypochlorite — is covered in LibertyCES's FRP Tank Resin Selection guide. Don't conflate the two resin questions — FRP resin-liner chemistry and polyethylene resin-family selection are governed by different mechanisms.
Chemical Storage Tank Substitution FAQ
Is a Snyder HDLPE tank an approved equal for a Poly Processing XLPE sodium hypochlorite tank?
It can be, but only if the engineer of record is shown the real, documented disagreement between the two resin families for this specific chemical — not a claim that they are simply interchangeable. Snyder's own accelerated-aging test data shows HDLPE outperforming XLPE for sodium hypochlorite exposure, while Poly Processing and Assmann both build their hypochlorite guidance around XLPE or LLDPE. This is a genuine, unresolved cross-manufacturer position, not a settled industry consensus, and a substitution request should present it as such rather than asserting one resin is simply better.
What is the real difference between IMFO and a SUMO fitting?
Both solve the same problem — getting a chemical storage tank to fully drain so salts and residue don't build up and corrode the tank or crystallize in the outlet — but with different hardware. Poly Processing's IMFO (Integrally Molded Flanged Outlet) is molded into the tank itself, in the same material, during manufacturing. Snyder's titanium SUMO fitting is a separate, bolt-on drain fitting recommended for periodic flushing (roughly every 6 months). Neither is a strict physical equivalent of the other — a substitution request should confirm the receiving piping and support structure are compatible with whichever fitting design is proposed.
Why do all three tank vendors specify titanium fittings for sodium hypochlorite?
Because standard metal fittings introduce transition-metal contamination (iron, copper) that independently accelerates oxidation and off-gassing in sodium hypochlorite — a mechanism all three vendors describe consistently even though they disagree on the tank resin itself. Titanium eliminates that exposed-metal pathway. This is one of the genuinely consistent findings across this comparison, not a point of disagreement.
What vent size should a sodium hypochlorite storage tank use?
Assmann's own published guidance states the vent should be sized at 2x the largest inlet fitting, and that under-venting is one of the most common causes of tank failure — a real, specific, checkable rule. Poly Processing's and Snyder's captured literature for this comparison did not state an equivalent numeric vent-sizing rule, so confirm the exact requirement against the current tank drawing for whichever vendor is ultimately specified, rather than assuming the same 2x rule applies universally.
Preparing a chemical storage tank substitution request?
Send James your basis-of-design tank spec, the chemical and concentration, and the exposure conditions (indoor/outdoor, temperature) — I’ll lay out the real resin and fitting comparison for your specific service, not a generic chart.
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