SPECIAL TO PHC NEWS
62
phc April 2022 www.phcppros.com
BY PAUL TULLY
U
ntil the 1960s, mechanical engineers and plumbing designers specified hub and spigot cast-iron soil pipe joined with lead and oakum for drain, waste and vent systems in the vast majority of their commercial projects. With the introduction of the CISPI 301 standard, hubless cast- iron soil pipe offered material and labor savings to plumbing contractors while still providing a durable, reliable system. PVC piping systems, first installed in Germany in 1934, began appearing in multistory buildings in the late- 1960s and 1970s here in the US. However, PVC piping systems were primarily used in single-family and some multifamily applications during that time. Then, beginning with the Great Recession in 2008, many commercial contractors offered PVC as a value-engineered alternative to project owners to lower construction costs. Today, while the plumbing industry still debates whether to use cast-iron soil pipe or PVC on a particular project, a new, even lower-cost alternative is being introduced on many commercial projects-cellular core PVC. Within 60 years, a relatively short period in the history of plumbing, commercial DWV systems have been value engineered from hub and spigot cast-iron soil pipe to foam core PVC. Is the latest proposed alternative the right choice for commercial plumbing?
Cellular core PVC
Schedule 40 PVC cellular core pipe, commonly referred to as foam core pipe, is manufactured to ASTM F891, Standard Specification for Coextruded Poly(Vinyl Chloride) (PVC) Plastic Pipe with a Cellular Core. This specification covers coextruded PVC plastic pipe with a cellular core and concentric inner and outer solid layers and is produced using a multilayer coextrusion die. Product manufactured to this standard consists of a foamed PVC core and two thin skins of solid PVC. The term "foamed core" refers to the fact that in the extrusion process, a blowing agent is added to the PVC in the center layer. This blowing agent displaces a significant amount of PVC resin. In essence, cellular core pipe has less PVC than solid wall PVC pipe. Cellular core PVC pipe is listed for gravity systems only and not rated for pressure. The print line on the pipe generally includes terms such as "COEX," "CELLULAR CORE" and "NOT FOR PRESSURE." Cellular core pipe technology was developed in France in 1979 by Alphacan, a large, multinational pipe company. Alphacan introduced cellular core pipe into the French market in 1982, and the product quickly gained acceptance and market share. The manufacturing process resulted in a pipe that was less expensive, lighter in weight and easier to cut. By the late-1980s, cellular core PVC pipe was produced regionally in parts of the United States by various pipe manufacturers, and it attained
While the plumbing industry still debates cast-iron soil pipe or PVC, a new, even lower-cost alternative is being introduced on many commercial projects.
Value Engineering Commercial DWV with Foam Core PVC
The term "foamed core" refers to the fact that in the extrusion process, a blowing agent is added to the PVC in the center layer. This blowing agent displaces a significant amount of PVC resin.
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