5 minute read
The PEX Effect
from CCR July 20
The PEX Effect 5 applications you need for your next multifamily project
By Kim Bliss
The construction industry is seeing a shift from metals to PEX for commercial plumbing and mechanical applications, especially in multifamily and hospitality projects. These types of structures are ideal for PEX, a flexible, durable polymer piping product that has been used since the 1970s in radiant heating applications, the mid-1990s in plumbing applications and for the past several years in mechanical hydronic heating and cooling applications.
PEX’s biggest benefit is its ease of use and durability for greater longevity. PEX is flexible and is available in coils up to 1,000 feet in length, so it is faster and easier to install compared to rigid metal and plastic pipes that require a fitting with each change in direction. With PEX, the installer simply bends the pipe to make a direction change. It also is highly durable, does not pit, scale or corrode, and its flexibility offers greater resistance to damage in freezing conditions. While no pipe is freeze-proof, PEX has the ability to expand to accommodate frozen water in the pipes and then contract back down after the water thaws. Since it is not an open-market commodity like copper, PEX offers more stable pricing that eliminates surprise changes from bid to actual installation, and it also
doesn’t have any scrap value, so it eliminates concerns of theft on the job site. PEX also supports job site safety since it is significantly lighter in weight than metal piping, so it is much easier for installers to move, and it does not require heat or open flame to make a connection. While there are several different connection methods available for PEX piping, including crimp, clamp, compression and push-to-connect, the ASTM F1960 expansion system is considered the professional’s choice since it cannot be dry fit and it is the only system that actually gets stronger over time. Lastly, PEX requires fewer nitrites, azoles and other chemicals to maintain a static hydronic environment for mechanical piping applications. This can prove highly beneficial not only during initial installation, but also for maintenance and a longer service life. Here are five key areas where PEX is ideal for use in hospitality and multifamily projects.
1. Risers PEX is available in sizes up to 3 inches for domestic water risers as well as mechanical piping risers. It is important to have the PEX manufacturer’s design team perform a proper design to ensure the pipe will meet the necessary requirements of the system and also provide long-term performance. In addition, be sure to support the pipe in accordance with local code and manufacturer’s recommendations. Like metallic piping systems, PEX also requires fire-penetration sealants. There are various products approved for use with PEX, including intumescent caulks, wrap strips, pass-through devices, collars and cast-in place sleeves. First, check with the manufacturer to confirm compatibility with PEX before installing.
2. Main piping PEX piping up to 3 inches is a great alternative to traditional metallic systems for horizontal main piping in low-rise to high-rise
commercial structures. Along with its ability to resist pitting, scaling and corrosion, the ASTM F1960 expansion fitting system can provide labor savings compared to copper sweat, steel groove or welding. To simplify piping support, a 9-foot steel support channel called “PEX-a Pipe Support” is available that allows for extended support spacing. Some PEX manufacturers also may have specific requirements for clamps and fixed points to help reduce linear expansion and contraction of the pipe. In addition, note that the fire-penetration information above also applies to PEX in main piping.
3. In-suite piping Due to its flexibility, PEX is superior for insuite applications where smaller-diameter pipe can easily bend with each change in piping direction. There also are PEX bend supports available to help keep the pipe in place when making a tight bend. For design options, designers can incorporate PEX into trunk and branch, homerun and structured layouts (also referred to as Logic). What is Logic? It is a design layout that maximizes the flexibility of PEX along with multiport tees (essentially a long tee with a bunch of ports) to minimize connections behind the wall. The logic design features a
main line going to a multiport tee with distribution lines going out from the tee. These individual lines extending from the single multiport tee provide water to all fixtures in a single or adjacent grouping. This style of design and installation vastly reduces the necessary piping versus a homerun system and significantly decreases the amount of fittings compared to a trunk and branch system. For example, in a typical multifamily structure, using a Logic design reduces the number of fittings by up to 70% when compared to trunk and branch and reduces piping by 40% compared to a homerun system.
4. Below grade or in the slab Because PEX piping is available in long, continuous lengths, it is ideal for running below grade or in a slab without fittings. (Always follow local code as some jurisdictions require additional sleeving and protection.) Some manufacturers offer a pre-sleeved PEX option with red and blue color-coded HDPE sleeving to distinguish between hot and cold domestic water lines. Regarding fittings in the slab, the ASTM F1960 fitting connection system is approved for direct burial. Note that brass fittings must be wrapped with an approved material before burial; however, engineered polymer (EP) fittings are approved for direct burial without an overwrap. Be sure to check with local codes and manufacturer requirements before installation.
5. Pre-insulated To save install time and money, there also are PEX manufacturers that offer a pre-insulated piping option with insulation thicknesses up to 2 inches to comply with local and national energy codes, including ASHRAE 90.1. This solution eliminates the two-step process of insulation after pipe installation. Manufacturers offer piping in sizes from ½ inches to 2 inches for both domestic water and mechanical piping applications. MH
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