Q&A: Using Dedicated Couplings to Join Pipes on New Construction Projects



Laying and connecting pipes in a new construction project is a complex and challenging task that requires careful planning and coordination. Some of the factors that need to be considered are:

  • The soil conditions and terrain of the site, as well as the presence of any obstacles or utilities that may interfere with the pipe installation.
  • The environmental and safety regulations that apply to the project, such as noise, dust, vibration, erosion, and waste management.
  • The layout and design of the pipe network, including the location of valves, joints, bends, branches, and outlets.
  • The quality control and testing procedures that ensure the pipe is installed correctly and meets the required standards and specifications.
  • The type and size of the pipe, as well as the material and fittings that are compatible with it.

Once the pipe has been lowered into the trench or borehole and is properly supported and secured, it is time to connect the pipe to the existing or planned network. Unlike municipal water distribution systems that have been in place for decades and expanded or repaired as needed, new construction projects have the advantage of planning the entire network from beginning to end. This means all elements can be ordered to specification and delivered for installation. Choosing a dedicated coupling that is quick and easy to use, can save a lot of time, and equally important is the type of material and design features that make some couplings last longer than others.

Ken Alessi, strategic product manager for HYMAX, a Mueller brand, answers commonly asked questions about the HYMAX Pro — a dedicated coupling designed to join the same diameter pipes without welding or special pipe fittings. This coupling is used in new construction projects and a variety of other applications, includingpenstocks, irrigation and industrial pipelines.


WF&M: What are the maximum and minimum allowable pipe sizes for these dedicated couplings?

Ken Alessi: They are available in nominal diameters from 4 to 24 in. The 4- to 10- in. sizes feature an industry-first, two-bolt, stab-fit construction. The 12- to 24-in. sizes have four top-facing bolts. Most couplings available in the market today need to be disassembled before they are installed. The HYMAX Pro coupling is designed to be installed onto the pipe and tightened to seal without disassembly and reassembly. This makes it easier and faster to install since bolts and end rings do not need to be loosened or removed. It also eliminates the possibility of components being dropped or lost. The bolts are pre-lubricated with a mag (molecular anti-galling) dry coating, so there is no need to lubricate the bolts, while also adding extra corrosion resistance.

WF&M: What types of pipe are commonly used in new construction and is the HYMAX Pro coupling compatible with these pipe materials to achieve a secure pipe connection?

Alessi: Today, the most common pipes in new construction projects use ductile iron or PVC (polyvinyl chloride) for water distribution systems, but in some industries or applications, steel and HDPE (polyethylene) are also very common. This coupling is designed for use with all these pipe materials, and more. It also has a hydraulically assisted gasket that allows flexible angular deflection of up to 4 degrees on either side of the coupling during installation, as well as dynamic deflection of 4 degrees post-installation. This feature enables high quality sealing even under unstable ground conditions and temperature fluctuations, reducing the risk of future breaks.

WF&M: Do you have any tips or recommendations for installation of the coupling?

Alessi: As with any pipeline project proper anchorage and restraint of the pipes is required for a proper installation; the HYMAX Pro does not restrain axial pipe movement. Additionally make sure the pipes are properly supported. Any well-designed piping system will take these factors, and more, into account. When joining any two pipes; clean and descale the pipe, mark the pipe, position the coupling for installation, stab it onto the pipe, and tighten the bolts with a torque wrench.

WF&M: What is the maximum pressure rating for this dedicated size couplings?

AlessiThe working pressure for the 4- to 14-in. couplings is 300 psi and the test pressure is 450 psi. The 16- to 24-in. couplings are  250 psi for working pressure and 375 psi for test pressure.Testing the pipe for leaks, pressure, flow, and alignment before the trench is closed is key for any successful installation.

WF&M: Are there any special considerations or limitations when using the coupling in high-velocity flow systems or areas with high vibration?

Alessi: No, it’s designed to handle most waterworks application. With the opening and closing of pumps and valves, it’s not uncommon for there to be surges in the piping system. The HYMAX Pro coupling has a hydraulically assisted gasket with two-stage sealing: mechanical sealing that is effective under vacuum or non-pressure. The self-inflating gasket   enables it to handle high-velocity pressure and transients.

WF&M: What certifications or approvals do the dedicated size couplings have from relevant regulatory bodies or standards organizations?

Alessi: All HYMAX Pro couplings conform to the AWWA C219, AWWA C213, NSF 61, and NSF 372 standards for drinking water system components.

WF&M: Are the couplings resistant to corrosion and chemicals commonly found in water systems?

Alessi: Yes, because of our long-standing history in the water industry, we use Grade 304 stainless steel hardware, and fusion-bonded epoxy coating as our standard to protect against corrosion.

WF&M: What is the expected service life of the couplings under normal operating conditions?

Alessi: HYMAX Pro couplings come with a two year limited warranty.  Having said that, I installed couplings in the 1970s that are still in service today, but it really depends on a variety of factors, including the installation and soil conditions, for example. Properly installed for the appropriate application, our HYMAX Pro coupling is built and designed for many years of use.