PEX underground plumbing system offers bagfuls of savings for grocery store chain

When Rice Building Systems of Sauk Rapids, Minn., set out to construct a new concept store for St. Cloud, Minn.-based Coborn’s Inc., they knew it would not be just another cookie-cutter project. For this store, located in St. Joseph, Minn., the owners wanted to capitalize on innovative materials and efficient design, while maintaining the 90-year-old Midwest grocery chain’s high standards for quality and customer service.

When plumbing bids went out, the cost for copper plumbing systems that were typical for other Coborn’s stores came back way too high. So, Rice sent out rebids, opening the doors to alternative plumbing materials, including crosslinked polyethylene (PEX) and CPVC.

“The owners wanted value engineering,” said Chris Rice, president of Rice Building Systems. “We knew any bid that came back had to incorporate suitable cost savings, in addition to intelligent design and efficient installation methods, to effectively meet our budget and tight construction schedule.”

Scott and Ben Kiffmeyer, owners of Kiffmeyer Plumbing Inc. in Sauk Rapids and 19-year veterans in the plumbing industry, had used PEX tubing in several previous installs and offered up a unique idea that would provide the value engineering that Coborn’s was looking for, while also conforming to the stringent construction schedule.

“Rice came back asking for ideas, and we went to them with the concept of running PEX underground,” said Scott Kiffmeyer. “That’s how we got the job.”

The underground PEX concept came from a presentation Kiffmeyer Plumbing received from Dean Corrigan of FourMation Sales and Casey Swanson, commercial sales representative from Uponor, a PEX manufacturer located in Apple Valley, Minn. Uponor also offers design and technical support for plumbing, fire sprinkler and radiant floor heating and cooling systems.

“They needed to get the plumbing system in quickly, so this was a great application for speeding up their construction schedule,” said Swanson. “It was also much more cost effective than doing copper overhead.”

The plumbing system, which used ½" through 2" Uponor AquaPEX® tubing for the 36,330-square-foot store, ran the PEX tubing underground instead of overhead as with a typical copper plumbing system application. The underground PEX system also incorporated Uponor’s unique engineered plastic (EP) fittings, which are approved for direct burial in soil. The fittings use a cold-expansion ProPEX® connection method, which uses a simple expander tool to make fittings, without the need for torches, glues, solvents or gauges.

According to Mike Rivers, technical support supervisor at Uponor and lead designer for the Coborn’s project, the plumbing system featured one cold-water main distribution header that fed three 2" supply lines and two 1¼" supply lines. The hot-water main line was 1½" PEX from the heat source, which was divided into three hot water zones for the deli/meat area, the bakery/produce area and the restroom area.

Rivers also noted that the project incorporated a few firsts in PEX commercial plumbing.

“The flush bank was all PEX, which is one of the first that we are aware of in the Midwest,” said Rivers. “Typically, these are installed with copper, but with PEX you have to increase the height of the header to allow for more play with the 1" lines that come down. Why do you have to allow for more play? We may need to explain this a little, although, if the audience is PHCC, this may not be necessary.”

Rivers stated that designers performed residual pressure calculations at both the farthest fixture and flush bank locations to verify that the system met minimum pressure requirements. “We had them hang the 2" header line 4' 6" off the floor with 1" pulls to the flush valves located 2' 6" below,” he said. “This allowed for less stress on the fixture connections.”

For the entire plumbing system, the install started in mid-August 2009, and the system was turned over in mid-November. “PEX provided great time and labor savings, which, in turn, offered great cost savings for the owner,” said Scott Kiffmeyer. “It was only 14 weeks from the day we started the underground installation to the day the store opened.”

Both Rice and Kiffmeyer estimate that installing PEX underground saved at least a week of installation time, as compared to installing overhead copper pipe. “On a grocery store project, saving a week is critical, especially toward the end of the construction schedule, when things start to pile up,” said Rice. “Also, having the plumbers in and out so fast gave us more time to have other contractors that we needed on the jobsite.”

Kiffmeyer echoed Rice’s sentiments. “The time saved from not having to work overhead in a lift was insurmountable,” he said. “Additionally, having the plumbing in so fast was a big help so that they could pour the concrete and stay on schedule. With Uponor PEX, we got the walls done faster, and they were able to sheetrock a lot sooner.”

Also, because the tubing was below ground and not overhead, the contractors weren’t in the way of the coolers and freezers that needed to be installed. “This is a concept store for Coborn’s, so they’re trying new technologies such as a colored concrete floor,” said Kiffmeyer. “It was important to have less traffic walking over the finished floor. Not having to worry about the mess of solder on the new floor was a plus as well.”

Both Kiffmeyer and Rice agree that the durability, flexibility and adaptability of PEX make it the ideal product for commercial plumbing installations; not to mention the incredible cost and time savings that the system afforded them. In fact, PEX was also approved for Rice Building Systems’ corporate headquarters in Sauk Rapids, which opened in 2010.

According to Rice, “After our experience with the plumbing installation in this concept store, PEX will most likely be the product of choice for more of our projects going forward.”