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The main difference between CPVC and PVC is the range of temperatures each is capable of withstanding. CPVC can handle temperatures up to 200° Fahrenheit, while PVC peaks at 140° Fahrenheit. Above those temperatures, both CPVC and PVC will begin to soften, increasing the risk of joints and pipes failing.
The primers, solvent cements, and bonding agents are different for PVC and CPVC due to the differences in their chemical composition. For example, CPVC solvent cements must meet ASTM F493 specifications, and PVC solvent cements must meet ASTM D2564 specifications. Because of this, CPVC and PVC pipes and fittings, along with their solvents and bonding agents, should not be used interchangeably. In addition to meeting ASTM specifications, there are different solvent cements required based on the pipe’s size and intended application, so check the product containers to be sure you’re using the correct agent for the correct application.
PVC comes in nominal pipe sizes only, while CPVC is available in both nominal pipe sizes and copper tube sizes. CPVC has greater flexibility than PVC, and requires support at three foot intervals to maintain its position.
Commonly used to create plumbing pipes and fittings, polyvinyl chloride is a man-made plastic with added stabilizers that prevent oxidation and degradation. As seen in the image below, PVC’s chemical composition is made of two carbon atoms linked together with a double bond and a perimeter of three hydrogen atoms and one chlorine atom attached by single bonds. This molecule is linked together with other molecules of the same makeup to form chains that are extruded into PVC.
Initially introduced to the US sewage, drainage, and water market in the 1950’s, there are more than two million miles of PVC pipe in service today. Because it is built to resist oxidation and degradation, PVC is highly durable. When properly installed, it is capable of a lifespan of 50 years or longer. Reasons PVC may fail are poorly glued joints or tree roots burrowing their way into the pipe.
For more on what is PVC, its characteristics and properies, read our resource article What is PVC | What is uPVC.
The color of PVC pipe is traditionally white or dark gray, with a technical description of the pipe printed on the side. PVC is available in both rigid form (commonly used in construction and piping applications) and flexible form (found in electrical cable insulation).1 It is safe to touch and handle, and does not leach chemicals when used as the manufacturer intended.
PVC can be cut with saws and glued to other PVC pipes and fittings without the need for heat or flame, such as that necessary to weld copper or iron pipes. For some applications you may determine a need to heat the pipe to make it more pliable- be sure to wear protective gloves, respirator, and safety glasses to prevent burns and exposure to fumes. When PVC discolors under heat, it is burning and all work should cease immediately to prevent excessive toxins from becoming airborne.
PVC has a peak temperature threshold of 140° Fahrenheit. For applications requiring temperatures above that, CPVC (chlorinated polyvinyl chloride) is recommended. CPVC offers some benefits over PVC, but at a slightly higher price point.
It depends on the application and local building codes. While both PVC and CPVC are suitable for water, gas, and drainage systems, many plumbers strongly recommend CPVC for hot water lines and PVC for cold water lines. Since PVC has a maximum temperature threshold of 140° Fahrenheit, its use isn’t recommended in applications where the temperature of the fluids it will carry or its ambient environment will go above that. CPVC would be recommended in these situations since its peak temperature threshold is 200° Fahrenheit. You may be surprised to learn that household water temperatures are not supposed to go above 140° Fahrenheit:
CPVC is a thermoplastic made via chlorination of the polyvinyl chloride resin. This means its chemical composition is two carbon atoms double bonded to each other, with two hydrogen atoms and two chlorine atoms single bonded to the carbon. This molecule links with others to form chains of CPVC. It is resistant to degradation and provides a long service lifespan. In fact, the first piping systems using CPVC occurred in 1959, and they are still working without a problem.
CPVC pipes are sized in two ways- nominal pipe size (NPS references the diameter of the interior hole of the pipe) and copper tube size (CTS references the outside diameter of the tube). Pipes using the NPS system are light gray, and pipes using CTS system are yellow. Both types of pipe will have their specifications printed on the side.
It is safe to use CPVC in applications where PVC may be used. Both PVC and CPVC have been deemed safe for potable water transport, i.e. cooking, drinking, and bathing water, and they’re resistant to degradation from acid, alkali, and most inorganic chemicals7. However, both materials require UV stabilizers or burial to prevent deterioration from the sun.
They’re both a quieter, easier to install, and less expensive alternative to copper and iron pipes, especially in plumbing applications. Because they are thermoplastics, they have an inherent insulation that reduces condensation formation on the pipes, and maintains water temperature (both cold and hot) better than copper pipes do.
They are available in the same lengths, with the same end shape options. Because their chemical composition contains a halogen- the element chlorine- their structure is stable and innately fire retardant. This stability also inhibits oxidation, giving both a long, useful performance life. Each material can be identified by pipe color and by reading the printing on the pipe.