An article on copper press fitting systems inspires a flood of questions.

In all my years of writing, I've found you never know what is going to turn on the readers. Articles that you think will make an impact could go nowhere. Sometimes, an article that is written for informational purposes receives a response that is phenomenal. That's just what happened when I wrote the article on copper press fitting systems ("Throw Away Your Torches," October 1999). I received hundreds of calls, e-mail messages and faxes.

There is an expression that says, for every call or message you receive, a hundred other people wanted to do the same. Whether true or not, there were a number of good questions asked regarding copper press fitting systems. Apparently readers' interests were piqued, and more information is desired.

To refresh your memory, the new fitting system is a press connection for copper tubing. The two companies that are currently distributing the fittings are Tubeline and Viega/Ridgid. The fittings have an internal O-ring and are joined by pressing the fitting to the copper tubing.

Questions & Answers

Without repeating the original information I provided, let me share with you the answers to the questions that were submitted regarding the press fittings.

The No. 1 question raised was: "What is the O-ring made of?" There were many follow-ups to this question such as, "Is the joint relying solely on the O-ring?" "Do you think the O-ring will last forever?" and "What happens to the O-ring after being in there for many years?"

The O-ring is a very important part of the copper press fitting system. That is why the manufacturers selected a high-grade elastomer for use in the O-ring. The O-ring material for the standard fittings is EPDM. This particular elastomer is one of the grades of plastic that hangs around forever.

Viega/Ridgid indicated that they use an even higher grade of elastomer that was designed for medical gas systems. Those fittings are not currently being offered in the United States, pending approval from the necessary agencies.

The copper press fittings do not rely entirely on the O-ring to make the joint. The first seal in the piping system is the copper-to-copper press connection. With 2,000 pounds of force being applied to the connection, the final result is a tight copper-to-copper joint between the copper tubing and fitting. Hence, the manufacturers have found the O-ring only sees water when the pressure of the system is on the high side. For lower-pressure water piping systems, the O-ring never sees any water.

"Can you move the pipe in the fitting after the joint has been pressed?" Believe it or not, the pipe can be rotated in the fitting, and the fitting still maintains the seal. The press fittings are actually tested for twisting and rotating after they are joined. This is to ensure the best possible connection. I do not recommend installing a system you think you can rotate afterward. However, if there is a problem in the initial layout, the fitting can always be rotated to correct an adjustment.


Many questions came in on the durability of the joint, the ability of the fittings to withstand abuse and their pressure rating, as well as questions on water hammer and hanger spacing. All of these queries indicate that you are thinking correctly.

The manufacturers inform me that the fitting goes through extensive testing. The actual testing requirements are a number of pages long. I don't want to bore you with the details, so let me paraphrase the requirements. The fittings are pressure tested to 800 psi under one test and 600 psi under another. The resulting pressure rating is 200 psi. I am sure the fittings could obtain an even higher rating, however, how high do we need a copper joint rated in a plumbing system? Most codes limit the pressure to 80 psi.

The fittings are also subjected to tests for water hammer (hydraulic shock), vibration, torque, pull out and hanging. The hanging, as I call it, is when they string a pipe between two supports and place a heavy weight in the middle of the pipe assembly. After sitting for some time, the joint is then tested to a high pressure. Hence, when supporting the piping system, you would use the same hanger spacing as a soldered copper piping system.

Water Flow

One reader happened to see a copper press fitting and noticed that the fitting and pipe have a hex shape after being pressed. He threw back to me the question, "You're an engineer, what happens to the water flow when it hits this fitting that is no longer round and has a hex shape? Should I worry about it?"

Anytime you change the shape of a pipe, it affects the flow of water. Hence, every time a fitting is encountered, the water flow is screwed up. What we tend to look at in the engineering profession is if the change in shape adversely affects the flow of water.

The answer is no. The normal flow parameters in a plumbing piping system are not seriously impacted by the hex shape of the finished fitting. The drop in pressure is minimal, to the point that you would not consider it in the design of the system.

"Are you aware that Victaulic has had a press fitting system for steel pipe?" another reader asked. Yes, I have been aware, and I have always liked the Victaulic system. I have never written about the system because it is typically used in process- and fire-sprinkler systems. I have tried to stay focused on plumbing matters.

The Victaulic system is actually the Mannesmann press fitting system. This is the same system used in the Tubeline copper fitting system. I had always hoped that Victaulic would have expanded the press fitting system into copper pipe fittings. Maybe now they will.

"What is the response of Nibco and other manufacturers?" I am sure they are watching. Don't be surprised to see other manufacturers come out with copper press fittings if these take off. That's how competition works in the United States.

The Bottom Line

"How much do the fittings cost?" From what I've been told, figure on average about three times the price of the cost of solder fittings for copper tubing. How much does the tool cost? Too much. From what I hear in the field, the power tool will cost over two grand for everything. Tubeline has a hand tool for press fitting its 1/2- and 3/4-inch fittings.

"Are the tools interchangeable between manufacturers?" If you ask the manufacturers, they will tell you that the press tools are not interchangeable. I asked a European familiar with both systems whether he used the tools interchangeably. He said that the Viega/Ridgid tool will work on the Tubeline fittings; however, the Tubeline tool will not work on the Viega/Ridgid fittings. Remember, the main difference in the fittings is the location of the O-ring in the socket joint.

One other point I should raise is one that has been stated by the manufacturers. They recommend that you mark the copper tubing after you place the fitting on the pipe. The mark is intended to indicate whether the fitting has pulled out prior to pressing the connection. This is based on the fact that most systems are completely assembled, then one person goes back and press fits all the connections.

Some of the solder manufacturers had less than kind words after reading my article. In response, I have not abandoned solder connections. I still like soldering, I continue to think that soldering will remain a part of the plumbing industry. The headline, "Throw Away Your Torches," was only intended to grab your attention, not to insult soldering.

I guess solder manufacturers feel the same way that lead and oakum manufacturers felt 30 years ago when somebody wrote an article about this new joint called the no-hub coupling. Progress happens, and I believe that copper press fitting is a positive addition to our profession. Whether it goes as far as no-hub coupling, only time will tell.