The Snyder Industries 3500 Gallon ASTM Black Captor Double Wall Tank is a tank-within-a-tank built for sites that cannot risk a release. It runs 158 inches tall on a 102 x 102-inch square footprint, molded from high density linear polyethylene with a black exterior that blocks UV and slows algae growth. The integral outer wall captures the full contents of the inner tank, which is why operators reach for this Snyder Captor double wall tank when secondary containment is the requirement rather than an afterthought.
Will it work for your install?
Plan the slab and the lift around real loaded weight, not the empty shell. Filled with water this tank carries roughly 29,190 lb, and Snyder rates it for contents up to about 55,461 lb at the tank's 1.9 specific gravity rating. That 1.9 SG is the buying reason, not just a loading caution: this is the dense-liquid, heavy-brine, containment version. If your liquid is at or near 1.0 like water, you are paying for density headroom you may not need; if it is a dense liquid above plain water, this is the correctly rated tank. Either way, engineer the pad, anchoring, and structural support to the rated contents weight, not the water number. Remember that 3,500 gallons is the nominal capacity - ASTM D1998 freeboard means your usable draw-down is less, so size to usable volume, not the nameplate. Run the Tank Sizing Calculator and the Tank Sizing Guide against your draw-down, and the Captor freeboard sizing guide per ASTM D1998 before you commit.
Fittings and access
Per the technical drawing on this page, this double wall tank is configured with a flange, an 18-inch PE threaded/vented fitting, and a manway with 15-inch access. The vented threaded fitting matters on a closed containment tank: gravity-fill and draw cycles move air, and proper venting keeps the inner wall from drawing a vacuum or building pressure. The 15-inch manway supports inspection and cleaning. Flange and bulkhead-style fittings on a poly tank seal through gaskets and correct torque, so confirm your gasket and seal hardware and follow Snyder's fitting torque sequence - on a captor vessel a weeping fitting defeats the secondary wall. Wall integrity is highest-stress at the vapor-saturated headspace above the liquid line, which is exactly where vented-fitting discipline pays off; the vapor-saturated headspace wall-thickness guide explains why those failures start where liquid-side inspection misses them. Match all fitting hardware against the technical drawing on this page so it fits what is molded in.
Freight and ordering
This is an LTL freight item shipped from Snyder plants in Lincoln, NE and West Virginia, with freight quoted live to your ZIP from the nearest plant rather than bundled into the listed price. A tank this size and weight ships on its own, so pull an exact number with the Freight Cost Estimator before you order and have a way to offload a unit of this scale at delivery. The single mistake to avoid is treating this like a single-wall water tank when you spec the slab and rigging - the captor design and 1.9 SG rating mean you build for the rated contents weight, not the water weight. For containment design context, read the Snyder Captor double-wall SPCC 40 CFR 112 walkthrough first; if this is going in as a rural or remote fire-water reservoir, the NFPA 22 fire-water reservoir design guide walks the sizing discipline. Questions on fit, fittings, or freight? Call 866-418-1777.
