The Snyder Industries 360 Gallon Double Wall Containment Tank is a tank-within-a-tank built for secondary containment, molded from High Density Linear Polyethylene with a 1.9 specific gravity rating. The outer wall provides backup volume to hold the inner tank's contents, so a leak or rupture stays contained instead of reaching the ground. It stands 63" tall on a 53" x 53" footprint in White opaque resin, covering the duty most operators mean when they search for a double wall containment tank: keep the stored liquid and its backup volume in one engineered unit. For water service, that same sealed double-wall construction also makes it a candidate for a fire-water reservoir or other clean-water storage where a single point of failure is not acceptable.
Will it work for your job
This is a 360-gallon primary tank with an integral containment shell. Filled with water (specific gravity 1.0) it loads to roughly 3,002 lb; the structure is rated to a maximum contents weight of 5,705 lb, so the 1.9 specific gravity rating means it is engineered to carry liquids up to 1.9 times the weight of water - the headroom you need for brines, concentrates, and many heavier industrial liquids. Plan your site for the full 53" x 53" pad and 63" of vertical clearance, plus room to work over the top, where the tank carries an 18" PE threaded and vented fitting and a manway with 15" access for filling, inspection, and service. See the technical drawing on this page for exact fitting positions and the inner-to-outer wall geometry before you set anchoring or plumbing. Match the tank to a known volume and weight with the Tank Sizing Calculator or the Tank Sizing Guide.
Sizing and freeboard
Double-wall containment tanks live or die on freeboard math: the outer wall has to swallow the full inner volume plus thermal expansion, and that changes how much usable capacity you actually get. Our guide on Snyder Captor double-wall freeboard sizing per ASTM D1998 walks through the thermal-expansion, chemistry, and density factors that decide your real working volume. If this tank is going into an SPCC program, the SPCC 40 CFR 112 compliance walkthrough shows where an integral containment unit fits the rule. Because the 1.9 rating is a specific-gravity number and not a density number, specific gravity vs density vs API gravity is worth a read before you size for a heavy liquid. For clean-water duty, the fire-water reservoir tank design guide covers NFPA 22 sizing discipline and cold-climate freeze protection.
The mistake to avoid
The 1.9 specific gravity rating is the structural ceiling, not a license to skip the chemistry. Confirm both the fluid weight (specific gravity) and the chemical service against the resin before filling - HDLPE handles many liquids but it is not universal. Just as important: the 18" PE threaded fitting and the manway with 15" access have their own limits. The PE threads and any manway gasket must be checked against your stored fluid separately from the HDLPE shell, because the gasket elastomer - not the poly - is usually the first thing a chemical attacks. Verify your fluid against the OEM chemical-resistance chart at your concentration and temperature, and check our chemical compatibility reference if you are storing anything other than water.
This Snyder containment tank ships LTL freight from the Snyder plant in Marked Tree, Arkansas, with the rate quoted live to your ZIP - get an exact number with the Freight Cost Estimator or call us at 866-418-1777. We will confirm fittings, freeboard, and delivery before you order.
