Wall thickness is not a critical measurement when considering the quality of a poly tank. Most poly tank manufacturers today mold their tanks with a variable wall thickness (thicker in some spots and thinner in others) to allow for deflection and performance. When comparing one manufacturer with another, consider the weight rating of the tank and the reputation of the company you are dealing with. More important than weight is the type of resin used, the design and engineering capabilities of the molder and the quality control processes in place. Lower grade resins also require thicker walls to compensate for their inferior physical properties.

Source: FAQs - Peabody