The Snyder Industries 3500 Gallon Captor Double Wall Tank is a black crosslinked linear polyethylene (XLPE) containment vessel built to ASTM standards for bulk storage that needs integral secondary containment. The tank-within-a-tank design puts the primary storage vessel inside an outer containment shell, so a primary breach is captured by the outer wall rather than reaching the ground. It stands 158 inches tall on a 102 x 102 inch footprint, giving you a full 3,500 gallon working capacity without spreading containment across a separate dike or berm. Before you trust that nameplate number, understand freeboard: a double wall tank's usable volume is not the full 3,500 gallons once you account for thermal expansion per ASTM D1998 — our guide to Captor freeboard sizing per ASTM D1998 walks through the real volume you can actually use. Run the dimensions through our Tank Sizing Calculator and review the Tank Sizing Guide before you pour the slab.
Will it work for your application?
This is a heavy unit by design. The footprint is 102 x 102 inches and it stands 158 inches — nearly 13 feet — so confirm door, roof, and overhead clearance before delivery and pad design. Filled with water it carries about 29,190 lb of contents, and at its full 1.9 specific gravity rating it is engineered to support up to 55,461 lb of stored liquid. That spread is the whole point: the 1.9 SG rating is what lets this Captor double wall hold heavy, dense solutions and not just water. Contents up to roughly 15.85 lb per gallon (1.9 SG) are within rating, so verify your stored liquid's density against that number before you order — it is the reason to choose the 1.9 XLPE Captor over a lighter-rated black double wall tank.
Fittings and tie-in planning
The factory fitting package shown on the technical drawing on this page includes a flange, an 18-inch PE threaded and vented fitting, and a manway with 15-inch access. Each serves a distinct role: the flange is your bulk fill and discharge tie-in, the 18-inch vented fitting must stay vented — do not cap it, since venting prevents vacuum or pressure buildup as you fill and draw — and the 15-inch manway is your inspection and entry access. Confirm fitting locations and elevations against the technical drawing before you finalize plumbing, because vent and flange placement drive how you tie fill, vent, and discharge lines into a double wall configuration. Make sure your fittings, gaskets, and seal materials are compatible with the stored liquid and rated for the service; gasket and seal material is the usual compatibility miss on an otherwise XLPE-rated tank.
The mistake to avoid
The most common error on a double wall tank this size is sizing to the nameplate gallons and ignoring freeboard, then discovering you cannot draw the full 3,500 gallons once thermal expansion headspace is accounted for. The second is treating the 1.9 SG rating as optional rather than verifying your liquid's density falls within it. Because the outer shell gives you built-in spill protection, these tanks are specified for SPCC-regulated sites under 40 CFR 112 — our SPCC compliance walkthrough covers how the Captor design fits that requirement, and the companion piece on wall thickness at the vapor-saturated headspace explains where premature failures originate. If this unit is going into fire-water or reservoir service, our fire-water reservoir design guide covers NFPA 22 sizing and cold-climate freeze protection.
This Snyder Captor double wall tank ships LTL freight from Snyder's Lincoln, NE plant, with West Virginia origin possibly applying for some regions, quoted live to your delivery ZIP. Get an exact number with our Freight Cost Estimator or call 866-418-1777 to lock in delivery. List price is shown above and excludes freight, which is quoted separately to your ZIP.
