Can PVC and CPVC be Glued Together?

Sch. 80 CPVC

PVC and CPVC have different applications, so they are not typically used in the same types of applications. CPVC goes through an extra chlorination process, which lets it withstand high temperatures much more effectively than regular PVC. While PVC starts deteriorating at 140F, CPVC stays strong up to 200F, which makes it perfect for water supply lines. PVC, on the other hand, is most often found in drain lines since it’s cheap and doesn’t rust. But if it was necessary, would gluing PVC to CPVC be possible?

Are CPVC and PVC Sizes Compatible?

The first thing to consider is size. Are the sizing systems even compatible? All major brand PVC pipe is made to NPS (Nominal Pipe Size) standards, or “schedules.” Schedule 40 and 80 are the most common NPS schedules. The schedule determines how thick the wall of the pipe will be. The size name (given in inches) is just a nominal size, so the measurements will not be exactly that size. A 1” schedule 40 pipe, for example, will have a 1.029” ID (inside diameter) and a 1.315” OD (outside diameter). Sch. 80 PVC and sch. 80 CPVC will fit together because they have the same ID and OD. The same is true of schedule 40 PVC and CPVC, but that type of CPVC is rarely used.

One major difference between these two types of piping, when it comes to sizing, is the fact that CPVC is made in two different sizing systems: NPS and CTS. CTS (Copper Tube Size) is, as the name suggests, the same size as copper piping. This is a source of confusion, as CTS CPVC and copper are both commonly used for the same jobs. CTS pipes and NPS pipes are not compatible. Usually CTS CPVC is yellowish in color, while NPS CPVC is gray (sch. 80) or off-white (sch. 40). They are also marked on the outside, so telling different types of piping apart should not be difficult.

Does CPVC to PVC Glue Exist?

Blue PVC Primer

Just because CPVC and PVC can fit together, this does not necessarily mean they can actually be implemented into a working system.PVC cement (or glue) does not work like regular glue. It breaks down the surface of the pipe it is applied to and chemically bonds pipes and fittings together. For this reason, you cannot use just any PVC cement to join these two materials together. CPVC, as we explained earlier, is a stronger version of PVC pipe with a higher melting point and tougher chemical structure. This means old-fashioned PVC cement will not be fully effective on CPVC.

There is no special “CPVC to PVC glue,” so chemically joining CPVC and PVC requires solvent cement and primer that are strong enough to fully bond CPVC pipe. To connect PVC to a CPVC fitting (or vice versa) follow these steps:

  1. Brush CPVC primer on the outside of the pipe and inside of the fitting about 2 inches deep.
  2. Immediately apply a light layer of CPVC cement to the area that is primed outside the pipe and inside the fitting.
  3. Slide and twist the pieces together then hold them together firmly for 30 seconds.

Should PVC and CPVC be Glued Together?

Sch. 80 PVC

Despite whether or not these two materials can be cemented and bonded to each other, the most important question is, “Why should you?” As we pointed out at the beginning of this post, PVC and CPVC, despite having three letters in common, have non-identical chemical structures which make them useful for different applications. PVC, with a max temperature of 140F is usually only used for drainage. CPVC, which can handle a balmy 200F, can be used for hot water lines as a low-cost alternative to copper.

The bottom line is that if you have a system that contains both PVC and CPVC parts, you will have to ensure its requirements are no greater than lowest common denominator of those components. In English: A system with both PVC and CPVC will need to remain under 140F. This leaves the CPVC underutilized. CPVC is more expensive than PVC, so there is rarely a justifiable reason to connect the two. It can be done if necessary, but it is essentially pointless. Making a system out of exclusively PVC would serve the same purpose and save money!

Additional information on adhesives for PVC pipe.