FRP: This is the most expensive of the tanks, and by far the strongest. Fiberglass tanks have a variety of different resins which can handle Sodium Hypochlorite, and are much better suited for handling high temperatures than either of the PE tanks. The down side for FRP tanks is that they are not proven to last any longer than the PE tanks for being more expensive. A tank leak can be very difficult to trace in this type of tank because it can start with a pinhole in the internal lining, and follow along the filament winding of the tank wall until it escapes outside the tank. A internal leak can be 180 degrees away from the point that the tank is leaking externally.
XLPE: Cross linking of the PE resin is done by means of a chemical reaction using Hydrogen Peroxide as a catalyst between 430-450°F. This process transforms the resin from being a thermoplastic to a thermoset. This gives it the added strength, but takes away the ability to weld to the tank. Many manufacturers believe that for larger tanks, the cross linking reaction does not completely occur throughout the tank wall. The best analogy for this would be trying to make a pancake that is too thick. The center is still raw and doughy. For a tank, this means that the exteriors of the tank walls are done, but the center is actually weaker than a linear HDPE tank.
HDPE: High Density Polyethylene tanks are the most cost effective of the options, and have not been proven to have any shorter life span than the above tank materials. The major advantage of this material is the ability to weld fittings, which diminishes the chance of leakage.
It is very important to note that for either type of PE tank, UV stabilizers should be used to prevent material degradation. For outdoor applications, we strongly recommend using a pigmented black color to the tank for added UV protection.