Residential plumbing uses different pipe materials for water supply and for drainage. Copper, PEX and CPVC are used for supply lines, while PVC, ABS and cast iron are common for drain, waste and vent (DWV) piping.[1] Older homes may still have galvanized steel, polybutylene or lead pipe, which can cause leaks or water-quality problems.[2][3]
Copper
Rigid copper tube comes in three wall thicknesses: Type K, the thickest; Type L, intermediate; and Type M, the thinnest and most common, identified by green, blue and red markings respectively.[4] Most copper corrosion problems result from poor workmanship, such as excess flux or inadequate flushing, and dielectric fittings prevent galvanic corrosion where copper meets other metals.[4] Soft, acidic water can dissolve copper, causing blue-green stains, a metallic taste and pinhole leaks.[5] Because of copper's cost, soldered copper is becoming less common in new homes.[1]
PEX
PEX (cross-linked polyethylene) is a flexible supply pipe joined with solderless crimp connections and increasingly accepted by plumbing codes.[1] A 2014 study led by Purdue University found that several brands of new PEX pipe raised odor in drinking water above the EPA's recommended limit, with results varying by brand.[6]
CPVC, PVC and ABS
CPVC is used for hot and cold supply lines. PVC is used for cold supply and, typically as Schedule 40, for drain, waste and vent piping, but it is not rated for hot water. ABS, a black plastic joined with black cement, is used only for drainage.[1]
Cast iron and galvanized steel
Cast iron is used for drain, waste and vent piping.[1] Galvanized steel supply pipe, common in older homes, can contain lead and can also collect lead from other sources, such as an upstream lead service line, and later release it into drinking water.[2][7]
Polybutylene
Polybutylene is a plastic pipe made from a by-product of oil refining. Homeowners alleged that it degraded in chlorinated water and leaked, and in 1995 a Tennessee court approved the national Cox v. Shell class-action settlement, under which Shell and Hoechst Celanese contributed $950 million to replace leaking systems and pay for damage.[3] The settlement covered systems installed from January 1, 1978, to July 31, 1995; polybutylene pipe is usually gray.[8]
Lead pipe and solder
Before 1986 there were no federal limits on lead in plumbing. The 1986 Safe Drinking Water Act amendments limited pipes to 8% lead, and the Reduction of Lead in Drinking Water Act of 2011 lowered the limit to a weighted average of 0.25% on surfaces that touch drinking water, with solder and flux limited to 0.2%.[9] Copper plumbing installed before 1991 likely used lead solder, and brass fixtures can leach lead even in homes with plastic pipe.[2]
References
- ^ ^ ^ ^ ^ "Piping & Fittings". Building Maintenance & Construction, University of Hawaiʻi Maui College. pressbooks-dev.oer.hawaii.edu
- ^ ^ ^ "Lead in Drinking Water". Penn State Extension, updated August 1, 2024. extension.psu.edu
- ^ ^ "Richard v. Hoechst Celanese Chemical Group, No. 02-41377". U.S. Court of Appeals for the Fifth Circuit, December 19, 2003. ca5.uscourts.gov
- ^ ^ "Corrosion of Copper Pipe and Fittings" (Publication No. 35). Connecticut Department of Public Health, November 2009. portal.ct.gov
- ^ "Corrosive Water Problems". Penn State Extension, updated May 29, 2025. extension.psu.edu
- ^ "Drinking water odors, chemicals above health standards caused by 'green building' plumbing". Purdue University, October 20, 2014. purdue.edu
- ^ "Sources of Lead in Drinking Water". U.S. Environmental Protection Agency, August 2017. epa.gov
- ^ "Polybute Settlement Money Still Available". Contractor, October 1, 2003. contractormag.com
- ^ "Use of Lead Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water". U.S. Environmental Protection Agency. epa.gov