Large-Diameter Sewer Pipe: PVC vs. Fiberglass — What You Need to Know
Choosing the Right Pipe Material Picking the right pipe material is a big deal — it directly impacts how cost-effective and reliable your sewer system will be for decades to come. For large-diameter gravity sewers, solid-wall PVC (polyvinyl chloride) and fiberglass (FRP) are two of the most commonly used options. While some engineers still think of 18-inch pipes as “large-diameter,” ASTM standards have included sizes up to 36 inches since 1986 — nearly 40 years ago! For this comparison, we’re focusing on pipes ranging from 24 to 60 inches — sizes you’ll commonly find available in both PVC and FRP. The Big Difference: Deflection The main thing that sets these two materials apart is how they handle ring deflection when buried underground. Here’s the key point: PVC pipe can handle significant deflection without any risk of material failure. FRP pipe can only tolerate small amounts of deflection — push it too far and it can crack or fail. So, if you’re designing with FRP, you’ll n...