Cast Iron vs. PVC - How Much Would You Pay for Quieter Pipes?
What may be a cost-effective solution is not always what it seems. I was involved in the plumbing design for an eight-story residential assisted living facility in Cambridge, Mass., where the architect insisted on using Polyvinyl Chloride (PVC) piping throughout for the sanitary and storm systems. The architect had convinced himself that PVC piping, on a cost-per-linear foot basis, was so much cheaper than cast iron and copper that it was ludicrous to consider cast iron as a material of construction for his project. He was quite justified in his thinking, given that lengths of PVC Schedule 40 piping are about one-fourth the cost of hubless cast iron.
My main concern at the time, however, was PVC's lack of sound attenuation. I finally succeeded in convincing the architect to accept cast-iron piping from the basement up to the second floor. Because the first floor contained all of the public areas and common living areas, the architect conceded that the flow noise of water cascading through the sanitary and storm piping would be unacceptable. In hindsight I've found that cast-iron piping probably could have been used for all of the vertical risers up to the eighth floor for nearly the same cost as PVC, with much quieter results. The following article is a qualitative and quantitative comparison between PVC and cast-iron installations.