To determine whether PVC or CPVC pipe is better for your project, you need to look at the hard limits of the project and what either pipe material can withstand.
If you are working with temperatures above 140° Fahrenheit, CPVC is your only option. PVC begins to soften around this temperature, while CPVC can handle temperatures up to 200° Fahrenheit.
Unless you need the slightly stronger material, PVC pipe works well for most residential applications and systems that are not subject to high temperatures. PVC pipes are often cheaper than CPVC, so you can cut some money out of your budget by going with PVC.
There are tiny differences that can make one better than the other for your project, and we’ll explore what you need to know right here.
The Basics of PVC Pipes
PVC pipe uses man-made polyvinyl chloride to meet certain plumbing needs. This material includes stabilizers that prevent oxidation and degradation, making it a reliable choice for many projects.
The United States adopted pipes for sewage, drainage and water in the 1950s, and it is now the most prominent pipe material for these reasons. PVC pipes use the Nominal Pipe Size (NPS) sizing standard, which means the size refers to their inside dimensions.
PVC remains one of the most suitable pipe materials out there and has a long history of use to back it up. You can identify it by its white or dark gray color, as well as by the technical specifications printed on the pipe.
Basic elements of CPVC pipes
The material used for CPVC pipe is same as PVC but modified by a chemical reaction to increase the chlorine level. This adds to the manufacturing process, but also makes the pipe more suitable for certain temperatures and chemical transport.
This process has not been patented until 1958and the material was not field tested until the 1960s. Samples taken from installing CPVC in research houses at the time were valid over 3 decades later.
CPVC pipe also uses NPS sizing, but some CPVC pipe uses the same copper tube size standard. Most CPVC pipe is light yellow or light gray (depending on its schedule). These colors usually indicate which size standard is being used, but it’s important to double check.
PVC vs CPVC: What’s the difference?
Middle the difference between PVC and CPVC pipes it is their composition and how they are made. Although they have the same basic structure, the manufacturing process for CPVC increases the chlorine content, hence the name chlorinated polyvinyl chloride.
This may seem like a minor difference, but it affects almost everything about pipes, including:
- Chemical resistance
- Lifespan and durability
- The joint systems they use
- Sizing standards
- How flowing water is affected
- Acceptable temperature range
- Budget
While you can use them interchangeably in some situations, it’s best to stick with one type of pipe for easier installation and troubleshooting.
1. Composition and manufacture
The raw material of PVC comes from salt and oil. The salt water is electrolyzed to produce chlorine, which is then mixed with the ethylene in the oil to make the vinyl chloride monomer.
The molecules of this material are then polymerized to make PVC resin before additives customize the compound. To make the shape of the pipe, you need to melt PVC pellets and then extrude them through a die, allowing enough time for cooling before cutting.
CPVC follows this manufacturing process, but has higher levels of chlorine due to a free radical chlorination process. To do this, manufacturers add chlorine to the PVC material, then initiate the reaction (usually with ultraviolet light).
This results in 40% of the bonding sites filled with chlorine atoms in CPVC, while PVC only has about 25% of the bonding sites filled with chlorine atoms.
2. Chemical resistance
Both PVC and CPVC pipes offer outstanding chemical resistance. Both materials are unlikely to degrade on contact with:
- ACID
- alkalis
- Inorganic chemicals
Also, both require UV stabilizers for use above ground and are better suited for non-exposed installation.
The extra chlorine in CPVC pipe makes it stronger as well resists well against aggressive acids.
On the other hand, PVC may perform better against ammonia and some amines, which are highly reactive with chlorine. If these materials come into contact with CPVC, it is possible to initiate rapid dehydrochlorination of the pipe material.
3. Lifetime and Durability
PVC pipe is one of the most popular pipe materials for a reason. When installed correctly and well maintained, PVC pipe is expected lasts an average of 100 years. This has yet to be proven true (as PVC pipes were only introduced 60 years ago).
Some factors that accelerate the deterioration of PVC pipe include:
- solar exposure
- debris and weather damage (ie frost)
- Improper installation or use
While CPVC is known as a more durable material, pipes are only expected to last 50 to 75 years under the right conditions. They suffer from the same concerns as PVC, but their tendency to embrittle when compromised poses a greater threat.
Otherwise, both materials are extremely tough and likely to withstand general use.
4. Common systems
PVC and CPVC pipes use different primers, cement and jointing materials due to the difference in chemical composition. PVC solvents must meet ASTM D2564 specifications, while CPVC solvents meet ASTM F493 specifications.
Even with PVC and CPVC pipes of the same size, you cannot mix joint materials as you see fit. Different compositions and standards do not react in the same way, and this leads to weak and incomplete connections.
6. Application
Both types of conduit work well for most applications, including:
- Commercial and recreational building use
- Cold water systems
- Ventilation systems
- Drainage systems
For this reason, you are more likely to see PVC due to its lower price and easier use.
The pipes must meet NSF standards by third party testing for proper use in water supply lines. While PVC and CPVC pipes can both meet these standards, most consider CPVC a safer material that exhibits greater resistance to chemical leaching.
The main difference in application is the use of CPVC for hot water plumbing. Its stronger construction also makes it the better choice for factories where pipes may come into contact with harder materials.
5. Sizing standards
PVC pipe uses Nominal Pipe Size (NPS) to label pipe sizes. This number indicates the inside diameter of the pipe, as opposed to outside diameter measurements.
CPVC pipes can use either NPS or Copper Tube Size (CTS). CTS refers to diameter outside of the pipe.
Both pipes offer a standard length of 10 feet, but only PVC pipes offer standard lengths of 20 feet.
The color of CPVC pipe usually indicates which sizing system is used. NPS CPVC (Schedule 80) is usually light gray in color, while your light yellow pipe is usually CTS gauged pipe.
7. Applicable temperature range
Neither PVC nor CPVC pipes perform well in freeze-thaw conditions and are not suitable for installation where freezing temperatures are expected. Anything below 32° Fahrenheit is likely to cause cracks or burst pipes.
PVC pipe has a lower heat threshold at 140° Fahrenheit, while CPVC pipe can withstand temperatures up to 200° Fahrenheit. Since most water heaters exceed this limit, you are more likely to see CPVC connections.
8. Budget
Due to its simpler manufacturing process, PVC pipe is cheaper than CPVC pipe of the same size and length. For example, 10 feet by ¾ PVC pipe can run $8while CPVC of similar size it costs about $12.
Fittings will probably follow the same price trend, but joint compounds cost about the same. Because CPVC is more flexible than PVC, you need to provide more support (every three feet), which is within your budget.
Both materials are cheaper than other popular pipe materials, including copper and iron, and are great considerations for repairs and economical projects.
Can you use PVC and CPVC interchangeably?
In theory, PVC and CPVC pipe and fittings using NPS sizing will fit perfectly together, but we recommend not using them together.
The first problem is that solvent cement for PVC and CPVC meet different standards and contain different chemicals designed to soften the surface of the pipe. By using the opposite solvent, you compromise the integrity of the joint.
This also interferes with the acceptable pressure and temperature values of your pipeline. Not only is a mixed system automatically weakened to lower values, but compromised joints are bound to reduce its potential.
Using the same pipe material and schedules is the safest way to transport the material. It also makes it easier to diagnose problems and make repairs in the future.
Conclusion
PVC and CPVC pipes are more similar than different. Both are thermoplastic materials commonly used in sanitary structures such as irrigation systems. They are cheap plastic pipes that are easy to work with.
The difference in acceptable temperature is the biggest difference between PVC and CPVC. While most other applications are a problem, any project exposed to higher temperatures (such as fire sprinkler systems) is better off with CPVC.
Comment with any questions you have about the difference between PVC and CPVC pipes.
