35 Gallon Double Wall Containment Tank, 22" Dia x 36"H, 6" Vented Manway

The 35 Gallon Double Wall Containment Tank (22" Dia × 36" H with 6" Vented Manway) is a heavy-duty, self-contained chemical storage and dispensing vessel designed specifically for commercial aquatic facilities, industrial water treatment, and municipal chemical feed applications.

Engineered with a "tank-within-a-tank" architecture, it fulfills EPA, OSHA, and local commercial secondary containment mandates (EPA 40 CFR 264.175) without the need for external concrete dikes, catch basins, or separate containment berms. In commercial pool equipment rooms, it is the standard vessel for storing aggressive chemical feeds such as liquid sodium hypochlorite (12.5% chlorine), muriatic acid (31.45% hydrochloric acid), sulfuric acid, sodium bisulfate slurries, and coagulants.

Mechanical & Structural Architecture

• Integrated Secondary Containment (110% to 120% Capacity): The outer containment tank is engineered to hold a minimum of 110% to 120% of the inner primary vessel's volume. In the event of primary tank failure, stress cracking, or internal fitting leaks, all chemical volume is captured within the interstitial annular space.

• Rotomolded Seamless Construction: Rotationally molded from high-density linear polyethylene (HDLPE) or high-density cross-linked polyethylene (XLPE). Monolithic molding eliminates seams, welds, and structural joints that are prone to environmental stress cracking under thermal expansion or aggressive chemical exposure.

• Heavy-Duty Specific Gravity Rating: Rated for specific gravities of 1.5 to 1.9 SG, easily handling heavy fluids like 31.45% muriatic acid (~1.16 SG) and concentrated 12.5–15% sodium hypochlorite (~1.20–1.22 SG).

• 6" Vented Access Manway: Features a 6-inch threaded or quarter-turn vented access lid with an internal splash baffle or breathable membrane. The vent prevents pressure buildup from chemical off-gassing (such as sodium hypochlorite decomposing into oxygen gas) while preventing vacuum collapse during rapid suction draw from high-output metering pumps.

• Molded Pump Mounting Flat: The top dome incorporates reinforced flat landing surfaces designed to directly anchor electronic metering pumps, peristaltic feeders, suction lances, and liquid level sensors without requiring external wall brackets.

• Visual Fluid Level Tracking: Molded in natural translucent white polyethylene, featuring embossed gallon and liter graduation marks down the sidewall for fast liquid level inventory checks at a glance.

Technical Specifications

• Nominal Primary Capacity: 35 US Gallons (approx. 132.5 Liters).

• Outer Containment Volume: Approx. 40 to 45 US Gallons (fulfilling $>110\%$ secondary containment requirements).

• Overall Outside Dimensions: 22" Outer Diameter × 36" Overall Height (approx. 55.9 cm Dia. × 91.4 cm H).

• Manway Access: 6" heavy-duty threaded polypropylene access cap with integrated pressure-relief vent.

• Specific Gravity Rating: Standard 1.5 SG (water/acid); heavy-duty 1.9 SG options available.

• Operating Temperature Limits: -20°F to 120°F (-29°C to 49°C) continuous service.

• Fitting & Port Provisions:

  • Top dome flats accommodate up to two 2" NPT female bulkhead fittings (for suction lances, return lines, or interstitial leak probes).

  • Optional bottom-drain containment transitions or top-draw-only suction assemblies to prevent gravity leaks.

Chemical Compatibility Reference

• Sodium Hypochlorite (12.5% – 15%): Fully compatible. The vented manway ensures continuous dissipation of liberated oxygen gas.

• Muriatic Acid (Hydrochloric Acid, 28% – 31.45%): Fully compatible. Eliminates fuming into the mechanical room when plumbed with a sealed suction assembly.

• Sulfuric Acid (up to 50% concentration): Fully compatible at ambient temperatures.

• Liquid Coagulants & Polyaluminum Chloride (PAC): Fully compatible; non-staining surface prevents organic adhesion.