Differences Between PVC and CPVC Pipes Explained

People often wonder about the differences between PVC and CPVC pipes and fittings. Common questions include whether PVC is a less expensive alternative, if one can be replaced with the other, and whether the fittings are the same size. In reality, these two materials are quite different. Below is an explanation of their chemistry, uses, and distinguishing features.

The Chemistry of PVC vs CPVC

Both PVC (polyvinyl chloride) and CPVC (chlorinated polyvinyl chloride) are man-made thermoplastics composed of hydrogen, carbon, and chlorine. CPVC is created by taking PVC through a chlorination process, making it more rigid and tolerant of higher temperatures. The added chlorine in CPVC results in a more flexible material with better insulating properties, allowing for expanded uses in potable water systems, fire protection, and industrial piping applications.

PVC vs CPVC Pressure Ratings

The pressure ratings for PVC and CPVC change significantly with temperature. For example, ¾” Sch40 PVC pipe is rated at 480 psi at 73°F but has no high-temperature rating. The same size CPVC pipe has a similar rating at 73°F but is also rated for 100 psi at 180°F. This higher temperature rating allows CPVC to be used for both cold and hot water applications.

PVC Defined

PVC has been widely used for decades as an alternative to copper and cast iron for drain, waste, and vent (DWV) piping. It is commonly used in residential and light commercial buildings and comes in sizes ranging from 1 ½” to 6”. Various fitting configurations allow for smooth wastewater flow in gravity drainage systems. Both the pipe and fittings are white and are joined chemically by solvent welding.

Solvent Welding

Solvent welded joints are airtight and watertight, making PVC ideal for sanitary drainage piping. The joining method involves a cleaner or primer (mostly acetone) and cement applied to both the pipe and fitting. The joint sets in about 20 minutes and cannot be taken apart.

Common Uses of PVC

• ​DWV (drain, waste, and vent) piping
• ​Venting high-efficiency appliances such as furnaces, boilers, and power-vented water heaters (for flue gases below 130°F)
• ​Other cold water applications

CPVC Defined

Before the introduction of PEX (cross-linked polyethylene) tubing, CPVC was a dominant material for potable water piping, serving as a less costly alternative to copper and galvanized steel. CPVC pipe and fittings are typically milky in color, often with a yellow stripe. The joining method is similar to PVC but uses slightly different cement types. CPVC acts as an insulator, making it less likely to sweat and suitable for both hot and cold water supply systems.

The improved properties of CPVC allow for a thinner pipe wall, improving flow in pressurized systems and matching the outer dimension of copper and PEX tubing in nominal sizes up to 2”. Various types of pipe hangers and insulation can be used for all three types of pipe. Some mechanical fittings, like compression or push-connect, can join copper, PEX, and CPVC in repair situations.

Common Uses of CPVC

• ​Approved sprinkler piping material (orange) for fire protection systems in residential and certain low-hazard occupancies
• ​Hydronic HVAC systems for hot water and chilled water piping (dark gray-Sch40)
• ​Industrial piping applications (light gray – Sch80) for water and other fluids due to high corrosion resistance
• ​Reclaimed water systems (purple), clearly marked as non-potable but suitable for irrigation

Both PVC and CPVC have significantly impacted how we convey and conserve clean water. Although their uses differ, they are essential materials in modern plumbing and piping systems.

A resource for identifying different pipe materials, fittings, and their functions is Interplay Learning’s Plumbing Materials Overview course.