The Snyder Industries 4000 Gallon HDPE Vertical Liquid Storage Tank (SKU SII-7421100N43) is a 1.5-specific-gravity-rated white polyethylene vertical tank standing 104 inches tall on a 120 x 120 inch footprint. Built to ASTM standards for liquid storage, its 1.5 SG rating means the wall is engineered to carry contents up to 50,040 pounds maximum rated weight - well above the 33,360 pounds of a full water column. If you are sizing a vertical storage tank for water, fire reserve, or general liquid service, those two numbers tell you most of what you need before freight ever enters the picture.
Will it work for your application
Filled with water, this 4000 gallon tank holds roughly 33,360 pounds of liquid, and its structure is rated to a 1.5 specific gravity, giving headroom up to 50,040 pounds of contents. Confirm your pad or foundation can carry that full-water load plus the tank's own weight across the 120 x 120 inch base, and check overhead clearance against the 104-inch overall height before delivery - the 18-inch top fitting and manway lid add working room you will want above the dome for fill and access. The tank arrives with a flange outlet, an 18-inch PE threaded and vented fitting, and a manway with 15-inch access for inspection and cleanout. To work through capacity, fill height, and footprint against your site, run the numbers with our Tank Sizing Calculator and the Tank Sizing Guide; the detailed 4000 Gallon Vertical Liquid Storage Tank buyer's guide walks through the same decisions in depth.
Fittings and inspection access
Three points of access come on this HDPE vertical tank: a flange, an 18-inch PE threaded and vented top fitting, and a manway with 15-inch access. Match the flange and threaded-fitting connections to your plumbing before ordering adapters - the flange diameter is shown on the technical drawing on this page - and verify the vent path stays clear so the tank breathes as it fills and draws down. The 15-inch manway access is your route in for inspection, and on tall HDPE verticals the wall section to watch is the vapor-saturated headspace near the top, where premature failures tend to originate rather than on the liquid-wetted lower wall. Our guide on HDPE tank wall thickness at the vapor-saturated headspace explains why liquid-side inspection misses it and how ASTM D1998 sizing logic addresses it.
The mistake to avoid
The 1.5 specific gravity rating is a structural ceiling, not a license to fill with just anything. It means the wall is built for liquids up to 1.5 times the density of water - water itself sits at 1.0, so you have real margin for heavier liquids. But specific gravity governs structural load only; it says nothing about chemical attack on the resin, or on the gaskets and seals at the flange and 18-inch threaded fitting. Those elastomers, not the HDPE wall, are usually the first chemical-compatibility failure point, so verify gasket and seal materials against your liquid before service. This is a water-service listing, so for fire-reserve or general water storage you are well within the rating. If your service trends denser, needs secondary containment, or runs chemically aggressive, confirm SG and resin compatibility against the OEM chart first and review the Snyder Captor double-wall freeboard sizing guide for a double-wall, denser-chemistry path. For fire-water reservoir sizing on rural and remote sites, see our guide on NFPA 22 sizing discipline and freeze protection, and refer to the technical drawing on this page for exact fitting placement and dimensions.
This tank ships LTL freight from the Snyder plant in Chowchilla, California, and freight is quoted live to your ZIP - never bundled into the list price. As a single oversize LTL unit moving from California, buyers east of the Rockies should expect long-haul LTL, so quote early and keep destination details accurate. Get an exact number with our Freight Cost Estimator or call 866-418-1777 for a freight quote to your site.
