The plumbing industry has come a long way, and so have the tools and materials that plumbers use. Instead of cast iron drains and galvanized steel water lines, CPVC and PVC have become the new norm. From drain lines and plumbing vents to condensation drains and water lines, these materials are used in many different ways.
Because of how similar PVC and CPVC pipe are to one another, many plumbers and DIYers wonder if they can use CPVC cement on PVC pipe. The short answer is that it's best practice to only use PVC cement (often referred to as PVC glue) with PVC materials and CPVC cement with CPVC materials. While CPVC cement may get the job done with PVC initially, there's a good chance that the bond won't hold over time.
If you want to know more about if you can use CPVC cement on PVC pipe and some of the risks involved, keep reading! This article will also explain the chemical reaction involved with PVC cement and primer and why it's important to use the appropriate adhesives with the corresponding pipe.
What's the Difference Between PVC and CPVC Pipe?
Although PVC and CPVC look and sound similar, they are two different types of pipe materials. PVC stands for polyvinyl chloride and is a robust, lightweight, and durable type of plastic pipe. CPVC stands for chlorinated polyvinyl chloride and is also a type of plastic pipe material.
However, the fact that CPVC pipe is chlorinated makes all the difference in the world. It drastically increases the chlorinated content of the pipe, which significantly alters the chemical composition. As such, here are some of the differences between PVC and CPVC pipes:
• CPVC can withstand temperatures of up to 200 degrees while PVC can only withstand temperatures of up to 140.
• PVC uses the Nominal Pipe Size system, while CPVC can use this system or the Copper Tube Size sizing system.
• PVC pipe is white, whereas CPVC pipe is often an off-white, gray or yellowish color.
• PVC is fairly brittle and stiff, while CPVC pipe is fairly flexible.
• PVC pipe walls are thicker and denser than CPVC pipe walls, which is largely the reason why CPVC is more flexible.
• CPVC pipe has a higher tensile strength than PVC and is also considered more durable.
Because of these many differences in characteristics and chemical composition, PVC and CPVC require different cements and primers. It also means that you should never use PVC and CPVC pipe in the same run because it will essentially hold CPVC back from its full potential.
What is Pipe Cement, and How Does It Work?
Pipe cement, also referred to as glue, is an adhesive that you apply to PVC or CPVC pipe to connect it to fittings of the same material. The pipe cement creates a chemical reaction when it comes into contact with the pipe, and starts the bonding process.
PVC Cement
PVC cement consists of a number of resins, solvents, and stabilizers, and the main ingredient is polyvinyl acetate resin. PVC cement must meet ASTM D2564 standards in order to be used in plumbing, HVAC, and other applications.
PVC cement works by essentially melting tiny sheets on PVC surfaces. This happens when it comes into contact with the PVC primer, which should always get applied before adding the cement. As the PVC sheets melt, they fuse together and form an almost inseparable bond, similar to how concrete bonds together. However, the bond can be broken when PVC is exposed to heat exceeding 140 degrees.
CPVC Cement
CPVC cement works similar to PVC cement, but has different ingredients and chemicals. While polyvinyl acetate resin is the main ingredient in PVC, CPVC cement consists of nearly equal parts tetrahydrofuran and acetone. It also contains various solvents, fillers, resins, and stabilizers, which may or may not be the same as PVC cement, depending on which cement you choose.
Another key difference between PVC solvent cement and CPVC cement is that PVC cement acts more like a glue and CPVC solvent acts more like a true cement. It does this by softening, melting, and fusing CPVC pipe and fittings together when it gets applied to these surfaces. The CPVC glue also oozes into every crevice and crack in the pipes and fittings, further strengthening the bond.
CPVC cement also requires a primer to get the chemical process started, but the bond is nearly inseparable once the connection is made.
Is CPVC Cement Compatible With PVC Pipe?
Because of the chemical composition of PVC pipes and the various ingredients of CPVC cement, the two are not compatible. Therefore, you shouldn't try to connect PVC pipes and fittings together using CPVC cement. While the bond may hold for a time, it won't be long-lasting.
The reason that CPVC primer and cement don't form a lasting connection with PVC pipe is because the two are unable to bond. The cement and primer are unable to seep into every crack and crevice of the PVC materials, and it also can't melt and bond with the surfaces. Therefore, while CPVC may form a temporary connection with PVC pipe, it won't last forever or hold up under pressure.
Potential Risks of Using CPVC Cement With PVC Pipe
Here are some of the potential risks of using CPVC cement with PVC pipe. The same issues are also true of using PVC cement with CPVC pipe.
• When water pressure is too high, the bond can break resulting in a leak.
• High temperatures can free the poor bond between CPVC cement and PVC pipe and cause a leak.
• Cold temperatures can cause the bond to become brittle and crack, resulting in pinhole leaks.
• Old age will also cause wear and tear on the bond between CPVC cement and PVC pipe, resulting in cracking and leaks.
Best Practices for Using PVC Glue and Primer
Although you should never use CPVC cement and primer, that typically isn't an issue because there are plenty of high-quality PVC cements and primers to choose from. Be sure to choose products that meet ASTM D2564 standards and that are made specifically for PVC pipe and fittings.
Once you have the right materials, you always want to apply primer to both the fitting and the pipe. Then, quickly apply PVC cement to both the fitting and the pipe. As quickly as possible, join the two pieces together and give the pipe a quarter turn to help the primer and cement really seep into the PVC.
Hold the connection in place for a few seconds until the pipe no longer pushes back from the fitting. As long as you follow these simple steps and make sure the PVC cement and primer never get too hot or cold, as per the instructions on the can, you should have no problem forming water tight PVC connections.