PVC and CPVC Pipe Primer

Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) pipe joints and segments are commonly joined using solvent cements. The solvent cements are applied to the inside of the pipe fitting and to the exterior of the pipe end before inserting the pipe into the fitting. They contain plastic resin dissolved in organic solvents. When the cement is applied, it softens the surfaces of the pipe and the fitting, allowing the pipe to chemically fuse together with the fitting as the solvent evaporates out of the seam (See the CPVC Solvent Cement Common Product). Some local codes require that a primer be applied prior to application of the solvent cement. The purpose of the primer is to speed up the penetration of the solvent cement and the softening of the surfaces in order to make a stronger joint. Primers are composed of a similar mix of solvents as those in PVC and CPVC solvent cements, but lack the plastic resin. Many products have purple colorant added in order to easily confirm that a primer has been used. 

Unlike solvent cements, which are specific to the type of plastic pipe being joined, the same primers can usually be used on PVC and CPVC pipes. For potable water applications primers must be certified to ANSI/NSF Standard 61, which establishes maximum levels of certain chemicals with known health hazards that are allowed to leach into water for materials that come into contact with drinking water. It does not address the impacts of chemicals with no known health hazards or the combined impacts of multiple chemical exposures. 

Volatile organic compounds (VOCs) in PVC and CPVC primers are typically limited to 550g/L or less to meet South Coast Air Quality Management District (SCAQMD) Rule 1168 VOC limits for plastic adhesive primers. Rule 1168 is designed to limit the amount of VOCs that contribute to photochemical smog formation that can be present in products. Because this rule specifically addresses chemicals that contribute to smog formation, some VOCs like acetone, found to be common in PVC and CPVC pipe primers, are exempt from regulatory VOC content calculations. An additional concern with PVC and CPVC primers is the presence of the solvent tetrahydrofuran (THF), a carcinogen. While found to be common, at least one manufacturer now offers a product line that is free of THF.