The buzz in many parts of the plumbing world concerns one-step solvent cement. What you hear depends on what part of the country you’re in. Although the laws of physics are the same around the world, methods of joining plastic pipe surely aren’t.

BF Goodrich, for one, is vigorously promoting one-step solvent cement. The concept only applies to joining CPVC plastic pipe. This surprises many plumbers because their response is, “What’s the big deal! We’ve been joining plastic pipe in one step for years.” Of course, what they are usually talking about is PVC, not CPVC.

We need a little history lesson on how all of this fuss got started. When plastic pipe was first introduced, the manufacturers decided they had to have a joining method that was better and stronger than the joining methods for cast iron, copper and steel pipe. After experimenting with the various formulations, they understood that they could join the plastic into a common bond between the pipe and the fittings. The final assembly would have a molecular structure equivalent to one solid piece of plastic. To drive their point home, the joint was first called a solvent welded joint. The concept was that it was equivalent to a welded piece of plastic pipe.

The extrusion method for PVC and CPVC plastic pipe, however, produced a pipe with a very hard outer shell. Solvent cement could not penetrate the hard outer shell. Responding to this problem, three different solutions arose:

  • Clean the end of the pipe with an emery cloth similar to polishing copper tubing.
  • Use a chemical cleaner similar to self-cleaning pastes for copper.
  • Use primer.

The emery cloth soon disappeared in most parts of the country and the battle began between cleaner and primer.

What’s The Difference: I’m always asked, “What is the difference between cleaner and primer?” The answer is about 5 percent. The important ingredient in both cleaner and primer is methyl-ethyl-ketone. Cleaner will cause a breakdown of the pipe wall by 5 percent, primer will break down the wall by 10 percent. Simply stated, primer softens the outside wall more. Most plumbing codes require primer to be used prior to the application of solvent cement.

To make matters worse, many plumbing codes require the primer to be purple in color. I think one of the reasons they required the primer to be purple was to make plumbers look like slobs. Primer is required to be the consistency of water, hence, the purple goes everywhere, making the job look lousy. There is absolutely no technical reason why primer has to be purple. It was put in the code because someone thought it would be nice for an inspector to easily tell whether plumbers used primer.

In Indiana, the plumbers got so disgusted with purple primer that they complained to the governor, and the governor got rid of the color requirement. I would recommend that plumbers do that in every state. By the way, the inspectors didn’t have a problem with removing the color. They could still tell if primer was used.

In some areas of the United States, plumbers have long used the one-step process for joining PVC in DWV systems. Plumbers have been joining PVC for years without using any primer. But today, the pipe is extruded differently. Hence, the exterior shell is no longer so hard.

What About CPVC? Which brings us to the one-step solvent cement promotion for CPVC plastic pipe. Joining CPVC is particularly critical since the pipe is used for potable water distribution. As a result, the pipe is under continuous pressure.

There have been a number of horror stories reported for not using one-step solvent cement. I have listened to every one of these stories. They included statements such as: “Not every manufacturer supports one-step solvent cement.” “The one-step solvent cement is not recommended for temperatures below 40 degrees F.” “The one-step solvent cement is not recommended for large diameter pipe.” “It’s not as good as primer.” “There hasn’t been enough research.” “The research does not include every manufacturer of CPVC.”

I have had to sit through hours of testimony by individuals opposed to one-step solvent cement. It is interesting that those opposed to its use don’t support the use of CPVC to begin with. So why not make it difficult to use CPVC plastic pipe by opposing one-step solvent cement? The reality of the situation is that plumbing contractors who have been forced to use primer, have for years been pleading with the manufacturers to make the joining method easier. The two-step process of using a primer is a pain in the butt. Eliminating the primer would make it faster and easier to join CPVC.

So, does the one-step solvent cement work? Of course it does.

The manufacturers have responded by developing a very good product. One-step solvent cement has at least 10 percent CPVC resin and the ability to break down the wall 3 percent. Although the breakdown is less than the primer, it is related to the softer exterior wall of the pipe. The 3 percent is more than adequate for making a terrific joint.

Manufacturers have tested the stuff to death. Having reviewed all of the test data, literature, and technical information, I can say, unequivocally, that one-step solvent cement works. There is no technical reason for not using, or not accepting, one-step solvent cement.

To answer some of the critics, if you look on the back of any can of solvent cement, it warns you not to use when the temperature drops below 40 degrees F. Every plumber knows that you either make the joint in warmer weather, or you use low-temperature solvent cement. As far as joining 42-inch pipe, NO, they didn’t test pipe that large! But then again, the majority of the CPVC installed in plumbing systems is 2 inches in diameter or less. (That’s what they tested.)

BF Goodrich and the large pipe manufacturers would not support one-step solvent cement if it didn’t work. They have too much at stake to support a lousy product that could fail. With the big names behind it, you can be sure that one-step solvent cement performs very well.

I would encourage you to throw away the CPVC primer and switch to one-step solvent cement. After we get universal acceptance of CPVC solvent cement, we can attack the wimpier pipe, called PVC.