PVC (polyvinyl chloride) is a thermoplastic that is molded into different shapes and sizes to form pipes and fittings. It is cheaper and more effective to use compared to steel or copper.
Closely related to PVC is CPVC (chlorinated polyvinyl chloride). CPVC is basically a PVC homopolymer that has undergone a chlorination process to improve its physical and chemical properties.
The main difference between PVC and CPVC is the maximum temperature each can withstand before softening. PVC cannot handle temperatures above 1400 Fahrenheit while CPVC is capable of handling temperatures of up to 2000 Fahrenheit.
PVC is made up of 57% chlorine (mass percent) while CPVC is made up of up to 74% chlorine, although most commercial CPVC resins contain 63-69% chlorine by mass. As such, CPVC is able to withstand higher temperatures (2000 F) compared to PVC (1400 F) before softening.
No material between PVC and CPVC is better than the other. It all depends on the intended application. PVC will comfortably handle any fluids as long as its temperature does not exceed 1400 F. Above that all the way to 2000 F CPVC will be the best option.
PVC and CPVC should not be glued together. Apart from the fact that they have different temperature ratings, the primers, solvent cements and bonding agents for PVC and CPV are different.
PVC solvent cements must meet ASTM D2564 specifications while CPVC solvent cements must meet ASTM F494 specifications. PVC and CPVC pipes, fittings and solvent cements/glues should therefore not be used interchangeably.
PVC and CPVC pipes are of the same size. There are schedule 40 PVC and CPVC pipes (thin walls and low pressure limit) and schedule 80 PVC and CPVC pipes (thicker walls and high pressure limits) but both have the same outside diameter.
However, PVC pipes are only available in nominal pipe sizes while CPVC pipes are available in both nominal pipe sizes and copper tube sizes.
PVC and CPVC pipes are used in plumbing, electrical conduits, HVAC, irrigation systems, water distribution, industrial and chemical applications. The only difference comes when the fluid being transported is too hot where then CPVC becomes the material of choice.
Differences between PVC and CPVC
After that brief introduction, allow me to explain to your in more details the differences between CPVC and PVC pipes or just the material itself.
The following are the main differences between PVC and CPVC:
1. Material Composition
As I mentioned earlier, polyvinyl chloride (PVC) is a special plastic that is made to resist degradation through addition of stabilizers. CPVC on the other hand is an improved version of CPVC made possible through a chlorination process to improve its properties.
A PVC monomer (the smallest molecule in a chain that makes up a compound) is made up of 2 carbon atoms linked together by 3 hydrogen atoms and 1 chlorine atom in single bonds.
This monomer is then linked together with other similar monomers to form what is called a polymer (long chains of monomers). These polymers are extruded to form PVC products like pipes and fittings.
On the other hand, a CPVC monomer is made up of 2 carbon atoms linked together with 2 hydrogen atoms and 2 chlorine atoms. This monomer combines with others to form CPVC polymers.
Note: A carbon atom must have 4 bonds connected to it. That is why a chlorine atom replaces a hydrogen atom in a PVC monomer to form a CPVC monomer.
Compared to PVC, CPVC products have a longer lifespan since they provide better resistance to degradation.
2. Temperature Rating
Perhaps the biggest determinant of which pipe to use in as far as PVC and CPVC are concerned is their temperature ratings. And without a doubt this is the main difference between PVC and CPVC.
As I have already mentioned, PVC pipes and fittings can withstand temperature of up to 140 degrees Fahrenheit. On the other hand, their improved cousins (CPVC) can handle temperatures of up to 200 degrees Fahrenheit.
So what happens when say the fluid being transported by the pipes has a higher temperature than the pipe’s rating?
The pipe will soften but the problem will start to manifest itself around the joints. The glues used to bind the pipes together will just start to melt resulting in failure of the entire system.
If you have a project at home, maybe to replace your old cast-iron sewer line, PVC pipes will do just fine. The wastewater emitted from residential places is always under the 140 degrees Fahrenheit rating for PVC pipes.
Both PVC and CPVC can last for a very long time. On average, PVC pipes will last for about 50 years although they can last even longer depending on where they are installed and how well they are installed.
Pipes installed in areas where there are tree roots are likely to last for fewer years than pipes installed far from tree roots. Less physical activities like driving on top of buried pipes or even earthquakes will see pipes lasting longer.
CPVC pipes will however last longer than PVC pipes. Their chemical composition allows them to resist degradation more than PVC pipes and hence a longer lifespan.
This is therefore to mean that you can totally opt to install CPVC pipes for your sewer lines or irrigation system if you want a longer service, despite the application requiring low temperatures.
PVC pipes are also reactive to chlorine while CPVC pipes are not. This also contributes to the CPVC pipes’ ability to last for a long time.
Due to the high chlorine content in CPVC pipes, bacteria growth inside the pipes is limited whereas in the case of PVC pipes there is a higher bacteria activity.
4. Solvent Cements
The main reason it is not recommended to glue PVC and CPVC pipes together is because the two types of pipes need different types of solvent cements to be joined together. As I mentioned earlier, PVC solvent cements must meet ASTM D2564 specifications while CPVC solvent cements must meet ASTM F494 specifications.
Remember, a connection is only as strong as its weakest link. If you use PVC solvent cements to connect CPVC pipes, the overall temperature rating of the entire network of pipes will be 140 degrees Fahrenheit instead of 200 degrees Fahrenheit.
One of the main questions most people ask concerning PVC and CPVC is “Is a PVC and CPVC of the same size”? This may sound like a simple question but it isn’t.
Well, the simple answer is YES. PVC pipes and CPVC pipes are of the same sizes. But there is more than just that.
The confusion arises because PVC pipes only use nominal pipe sizes while CPVC pipes uses both nominal pipe sizes and copper tube sizes. The nominal pipe size of a pipe refers to its inner diameter while the copper tubing size of a pipe is its outside diameter.
As you can see, if someone is using the copper tubing size to refer to a 2-inch (nominal) CPVC pipe, you may think it is bigger than another 2-inch PVC pipe. The two pipes however have the same outside diameter.
Another thing to remember is that there are both schedule 40 PVC and CPVC pipes as well as schedule 80 PVC and CPVC pipes. I have written more about schedule 40 and schedule 80 pipes in this post.
In short, schedule 40 pipes have thinner walls compared to schedule 80 pipes. As such schedule 80 pipes are able to withstand more pressure compared to schedule 40 PVC pipes.
As an example a 2-inch schedule 40 PVC or CPVC pipe has an inside diameter of 2.047 inches while the same size of a schedule 80 PVC and CPV pipes have an internal diameter of 1.913 inches.
However both pipes have the same and equal outside diameter of 2.375 inches. Schedule 80 pipes just have thicker walls.
I should also add that both PVC and CPVC pipes are available in 10 and 20 feet lengths. They are also both available in plain ends and bell ends.
If flexibility is important to you like when you need to install a pipe around a curve, CPVC pipe is the clear winner here. It is way more flexible than PVC pipe.
I should mention that due to its flexibility a CPVC pipe will need to be supported at intervals of 3 feet. If that is not done the pipe will start to belly and put strain on the joints.
If I can tie ductility to this point, PVC pipes are less ductile while CPVC pipes are more ductile, allowing greater flexure and crush resistance.
In terms of tensile strength, PVC (both schedule 40 and 80) has tensile strength of 7500 psi while CPVC has a tensile strength of 8200 psi.
Most people get confused when it comes to colors and plastic pipes. Most of the PVC pipes you will see around in residential places will be white.
As a matter of fact, most people refer to PVC pipes as white plumbing pipes in a bid to distinguish them from the gray electrical conduit PVC pipes.
What you may not however know is that only schedule 40 PVC pipes are white. Anyway, those are the pipes used for residential plumbing.
Schedule 80 PVC pipes are gray in color and are therefore easy to confuse with gray electrical conduit PVC pipes.
Schedule 40 CPVC pipes are available in off-white or yellowish-cream color while schedule 80 CPVC pipes are available in light-gray color.
The easiest way however to identify these pipes is by checking the specifications which are always printed on the side of the pipe. You will see the type of pipe it is, the schedule and other useful information.
PVC pipes and fittings are less expensive compared to CPVC pipes and fittings. And that makes perfect sense.
The extra chlorination process in the conversion of PVC into PVC increases the cost of production of CPVC pipes and fittings. Both of these pipes are however way cheaper compared to steel and copper.
Both PVC and CPVC can be used in many different areas including but not limited to:
- Sewer lines
- Sprinkler systems
- Chemical applications
- Water distribution
- Electrical installations
It becomes critical when the fluid being carried by the pipe is hot. Without sounding repetitive, CPVC is better at handling hot fluids compared to PVC. Schedule 80 CPVC thanks to its thick walls is even better for hot pressurized fluids.
In a nutshell, PVC pipes are suitable for use in the drain-waste-vent system, irrigation systems, cold water systems, yard irrigation and sprinkler systems.
On the other hand, CPVC can be used in the above systems but it is better at handling hot water systems, water distribution, industrial liquid handling etc. It should also be your pipe of choice if you are in an area with corrosive water.
Can PVC and CPVC be Glued Together?
Yes. PVC and CPVC can be glued together, but you shouldn’t do it. Why would you even do it? It is not that cost-effective. The end does not justify the means.
As I have already mentioned, PVC pipes and fittings are of the same size. The 2 can therefore perfectly fit together. That does not however allow you to glue PVC to CPVC.
To start with, PVC and CPVC require different solvent cements (glues) to connect 2 pipes together. The glue binds the pipes differently, owing to the different chemical composition of the pipes.
PVC solvent cement works by breaking down the surface it is applied on to chemically bind pipes and fittings together. CPVC, having a higher melting point than PVC will need a different type of cement.
Since there is no special cement to join PVC and CPVC together, joining the 2 pipes is not a good idea.
Apart from that, CPVC and PVC have different temperature ratings. The best way to do things is to use the same type of pipes and fittings.
And basically those are the main differences between PVC and CPVC. I sincerely hope that this post was helpful.