Cylindrical - Open Top - Flat Bottom [COF]

Tanks - Cylindrical - Open Top - Flat Bottom [COF]

Saint-Gobain Performance Plastics high-performance tanks are the best and toughest in the industry. Exacting CAD-based designs, the highest quality virgin resins and tough construction provide excellent solutions for general purpose applications. The tanks are translucent and feature molded-in graduations.

Each tank comes with a matching cover the same thickness as the wall. The open-top unit covers fit like a shoe box; bolted or welded covers are available upon request.

Closed-dome tanks are available for applications requiring a completely closed vessel. The 6" threaded polypropylene covers prevent evaporation and spills. Our open-top tanks are rated for use with 1.8 specific gravity media. If a fiberglass casing is used, the rating goes up to 2.2. Casings provide structural support and prevent bulging at the bottom of the tank. They should be used with rectangular units with any dimension greater than 18 inches. Casings are also required for use with media having a specific gravity greater than 1.8 or for use at prolonged elevated temperatures.

Our stands, mixers, and casings have been pre-engineered for compatibility. Simply choose your tank size and the size codes of the accessories will match.

Fabrication is available for all Saint-Gobain Performance Plastics tanks. Modifications can be made to the covers or the sides. Welded and mechanical fittings can be installed, as well as a full line of accessories. Contact Us for quotations.


Materials Overview


High Density Polyethylene (HDPE)
  • FDA 21 CFR 177.1520
  • Hard, Smooth Finish
  • Very Good Chemical Resistance
  • Good Stress-Crack Resistance
  • Max Service Temp-140°F
  • Translucent White
Cross-Linked Polyethylene (XLPE)
  • Not FDA
  • Cannot be welded
  • Better Chemical Resistance to HDPE
  • Excellent Stress-Crack Resistance
  • Max Service Temp-140°F
  • Yellow (Bulk Tanks-Gray)


Polypropylene (PP)
  • FDA 21 CFR 177.1520
  • USP Class VI, Non-Cytotoxic
  • Hard, Smooth Finish
  • Very Good Chemical Resistance
  • Excellent Stress-Crack Resistance
  • Max Service Temp-220°F
  • White
Polyvinylidene Fluoride (PVDF)
  • FDA 21 CFR 177.2510
  • High-Purity Material/Low Extractables
  • Larger sizes require casings
  • Inherent UV Resistance
  • Excellent Chemical Resistance
  • Max Service Temp-230°F
  • Off-White


Maximum service temperature listings refer to temperatures that should not be exceeded for the materials utilized in the specific product line. Many factors including media, specific gravity of media, external stresses, product geometry, environment, and others affect suitability of material.

Structural Designs

Cylindrical tanks feature a stepped-flange design that adds rigidity and strength while helping to contain drips. Tanks over 30 gallons feature a slightly raised bottom that channels liquids to tank walls and fittings. Spoke bottoms reinforce larger tanks over 55 gallons and provide near-total drainage.


Guidelines for Open Top Tank Installations



Flat-Bottom Cylindrical Tanks

  • All tanks come with covers.
  • Brim capacity 10% over.

WARNING: Never use FRP casings alone as a tank. Always use a liner. For continuous service at elevated temperatures or storage of high specific-gravity materials, always use an FRP casing with your tank.

Flat-Bottom Cylindrical Tanks Chart (PDF)

Open Top Cylindrical Tanks

  • Every size, every shape in stock
  • Natural translucent resin permits visual determination of fluid level in the tank
  • All tanks are rotomolded from virgin, FDA-approved linear polyethylene
  • Tough, corrosion- and impact-resistant material

STI's complete inventory of top-quality rotomolded cylindrical tanks assures our ability to provide what you need, when you need it. A tank molded in virgin linear polyethylene is the ideal choice for storage, mixing and/or feeding a vast array of liquids.

The Open Top Cylindrical Tanks are ideal for a variety of applications including: water treatment, wastewater treatment, plating, process, 'tank-in-tank' systems for double containment of hazardous solutions, chemical feed day tanks (see CXF/CXC tanks for bulk storage), batch mixing and more.

Your application may demand the mechanical strength and chemical resistance to withstand the strongest acids, caustics, and other chemicals. You may need the cleanliness to handle the extremes of ultra-pure water; the purity to maintain ionic contaminants in the parts-per-billion range. Either way, our team of application specialists and plastic fabricators can put together the right system for you.

Available Tank Dimensions (PDF)