What is the minimum approved wall thickness for any approved steel septic tank?

The minimum approved wall thickness for any approved steel septic tank is indeed 12 US gauge. This standard is established to ensure structural integrity and durability in various soil conditions, as well as to withstand the pressure exerted by the ground and the weight of the tank contents. A thickness of 12 US gauge, which is approximately 0.105 inches or 2.67 mm, provides a good balance between strength and material usage, allowing the tank to maintain its shape and withstand environmental stresses over time. Using material that is too thin could lead to corrosion or structural failure, while excessively thick materials may unnecessarily increase costs without significantly enhancing strength. Therefore, 12 US gauge is the accepted standard for ensuring functionality and longevity of steel septic tanks in plumbing practice.