New Pipe Joining Methods
Over the past few years, there have been a number of new pipe joining methods that have either been introduced or accepted by the Plumbing Code. Virtually every plumbing piping material has seen the introduction of new joining methods.
One of the most exciting new pipe joints is press connect fittings for copper tubing. Before the introduction of press connect fittings, the only change to joining copper tubing has been the introduction of no-lead solder. The major effort to gain acceptance of copper press connect fittings has been by Viega. Their fittings are distributed by Ridge Tool Company. Two other major manufacturers of press connect fittings in Europe are IBP and Mannesmann. Both companies may soon have product available in the United States.
All three manufacturers utilize the same basic premise for making the copper press connections. The copper fittings have a cavity with an EPDM o-ring. The pipe is inserted into the fitting and a special tool presses the fitting to the pipe. The difference between the manufacturers is the location of the o-ring cavity. The Viega fittings have the o-ring located in the middle of the socket of the fitting. The other manufacturers' fittings have the o-ring at the entrance to the fitting.
It should be noted that the tool for one manufacturer does not work on the fittings of the other manufacturers. There are special jaws for each manufacturer's fittings.
The current product line in the United States includes a complete line of fittings in sizes 1/2 inch through 4 inches. The fittings 1/2-inch through 2-inch are available in both wrought and cast fittings. The larger fittings, 2 -1/2-inch through 4-inch are cast bronze fittings with a special stainless steel crimp ring in the socket of each fitting in addition to the o-ring.
This month, Viega introduces a new copper press fitting for fuel gas piping systems. The fuel gas fittings have a different o-ring that is rated for high temperatures. The fittings have a yellow coloring that distinguishes between a water fitting and a gas fitting.
Another nice feature in the gas fittings is a leakage path. If a contractor fails to press the fitting, the leakage path forces a leak in the system. Hence, the fuel gas piping system could not pass the pressure test unless every fitting is pressed.
Both the Uniform Plumbing Code and the International Plumbing Code permit press connect fittings. The water fittings are copper, brass, and bronze, meeting the requirements of NSF 61 for use in drinking water installations.
Copper press fittings are rated for a working pressure of 200 psi, however, every manufacturer has stated that the fittings will hold a much higher pressure. The temperature limitation is based on 250F for hot water systems and 395F for steam.
A new standard is being developed for copper press fittings. That standard is ASME B16.51. The standard will require a series of tests includes bending, torqueing, thermocycling, hydraulic shock, and exposure to high temperature.
The most severe test for the joining method is the thermocycling, which requires the joint to be exposed to 5000 cycles of hot and cold water. During the cycling, the joint is exposed to a pressure of 150 psi. No leakage is permitted during the testing.
For the torque tests, the fitting is rotated around the pipe. Most engineers have assumed that once the joint is made, the fitting cannot be moved. However, by use of a wrench, the fitting can be rotated after installation. While this is not a common practice, it accommodates minor changes in the direction of fittings after being press fit.
The beauty of the copper press fitting system is the speed of installation. Each joint is made in 4 to 7 seconds, depending on whether the contractor uses the battery tool or the line voltage tool. The battery tool is 3 seconds slower in making the press connection. The speed of installation far exceeds the labor rate for joining a solder system. New Solder Flux Are Getting Better A change to copper joints that is sometimes ignored is the requirement for compliance to NSF 61 for water distribution systems. This includes the solder and flux. While the solder has not changed, the flux has. The Plumbing Code requires flux for potable water to meet NSF 61. This requirement is also a part of many state health department requirements.
The problem associated with the new flux is the temperature limitations. Plumbing contractors have been getting away with being lazy in soldering copper fittings. The no-lead solders and old fluxes work wonders at virtually any temperature. The old flux typically had zinc chloride as one of the components. The temperature limitations on these fluxes was in excess of 900 F.
The new water soluble fluxes use organics instead of zinc chloride. As a result, they have a temperature limitation around 460 F (with some a little higher). This temperature is only slightly higher than the melt point of the solder. Hence, a greater skill is required to make the solder connection. If a plumbing contractor raises the temperature of the joint to above the maximum limits of the flux, some of the fluxes turn black and a good joint cannot be made. The only solution is to start over by cleaning and re-fluxing the joint.
Some manufacturers have done better with the water soluable fluxes than others. Contractors should experiment with the various fluxes that conform to NSF 61 to determine the flux best suited for their method of soldering. Cast Iron No-Hub The big dispute for the past few years has been what level of joining is needed for a no-hub coupling. Many varieties of couplings are available for joining cast iron.
The latest edition of couplings are the rigid unshielded couplings. Rather than having a metallic shield around the coupling, the couplings are a rigid thermal plastic material. Hence, the only metallic component is the bands to tighten the joint.
The concern regarding no-hub couplings is how much support the coupling is supposed to provide for the joint. When properly installed, the no-hub coupling should not be supporting the pipe. However, realistically, the plumbing industry recognizes that there will be a need to resist torsional movement in the joint.
The new standard identifies tests for determining the ability of the coupling to within anticipated forces in field installations. The new standard being developed by ASME to regulate these couplings is ASME A112.4.4. PEX Fittings Since the demise of polybutylene, there has been an emphasis on cross linked polyethylene (PEX) as the replacement flexible water piping material. As a result there has been a tremendous number of new joining methods introduced.
One of the original complaints about PEX was that the fittings and pipe had to be supplied by the same manufacturer. ASTM F877 required the pipe and fittings to be evaluated for the joining method. Within the past few years, many new fittings standards have been introduced that allow fittings to be used with any pipe. The 2003 edition of the Uniform Plumbing Code lists the following PEX fittings standards: ASTM F1807, ASTM F1960, ASTM F1961, and ASTM F2080. These fittings are crimp and insert type fittings. The newer fittings can be used on any PEX tubing.
That has not stopped other manufacturers from introducing other fittings that meet the ASTM F877 standard. One of the fascinating fittings is the Stadler/Viega fitting. Their fitting system uses bronze fittings with a press connection. Rather than a crimp ring, the fittings have a press cup that fits on the end of the tubing before it is inserted into the fitting. The press cup eliminates the need to line up a crimp ring. A small hole in the cup assures that the pipe is fully inserted into the cup and fitting. The cup is pressed to the pipe. PEX-AL-PEX Fittings Like PEX, PEX-AL-PEX has developed a standard for regulating fittings for joining different manufacturers' pipe. The fitting standard is ASTM F1974. This standard does not preclude the manufacturer from developing a special joining method for their particular PEX-AL-PEX pipe.
CPVC Solvent Cement The 2003 Uniform Plumbing Code has finally accepted one-step solvent cement for CPVC plastic pipe. One-step solvent cement has been popular for joining CPVC in sprinkler piping installations.
For the past few years there has been a major debate over whether primer is necessary. The purpose of the primer is to break down the outside wall to allow the solvent cement to make a firm bond between the pipe and the fittings. The change in formulation allows this process to be completed with a one-step solvent cement. All of the testing on one-step solvent cemented joins has proven that the joint is more than adequate for a plumbing water distribution system. PVC Solvent Cement With the acceptance of CPVC one-step solvent cement, there has been additional discussion on the need to use primer when joining PVC plastic pipe. In certain parts of the country, including Florida, the use of primer on PVC has not been standard practice for many years.
Attempts have been made to gain code acceptance for joining PVC without the use of primer, however, to date, all of the code changes have failed. That is not to say that joining PVC without primer doesn't work. In the parts of the country that have not used primer, there is not a massive number of failures of PVC joining methods.
Look for future research regarding PVC solvent cementing. Before the codes accept a change, the ASTM D2665 standard would have to be revised. But, the days of primer may be numbered. Nothing New With Steel In many ways, the steel pipe industry started the explosion of new joining methods about 25 years ago. The only method of joining steel pipe used to be threaded and welded joints. Today, there are numerous mechanical joints, rolled groove, and cut groove joints.
Most of the newer steel pipe joints started out for use in fire sprinkler systems. From there, the joints expanded to other piping systems. However, within the past few years, there have not been any new or exciting changes to joining methods for steel pipe.
Expect the trend of new pipe joining methods to continue. If it can cut labor time, reduce cost, or increase performance, expect to see new joining methods.
"This article was originally posted on ww.reevesjournal.com."