HK Turns Municipal Pipe Joint Testing Inside Out with the Straub Test Coupler

Hamilton Kent turned joint testing for concrete pipe and manholes inside out – quite literally – with the development of the Straub Test Coupler. While traditional joint testing involves filling the pipe with water and pressurizing it from the inside to test for joint leaks, the Straub test coupler is installed around the joint and applies pressure from the outside to test the joint’s ability to withstand hydrostatic pressure from the environment around the pipes.

The Straub Test Coupler dramatically simplifies joint testing for pipe and precast concrete producers and contractors and provides quality assurance to project owners that the joints will meet or exceed specifications.

It’s really the difference between exfiltration and infiltration, said Randy Reimer, Director of Sales and Marketing for Hamilton Kent. For decades, pipe joints have been tested for their ability to contain liquids flowing through without leaking. Large pipe systems, however, rarely experience high flow levels that would create high pressure inside the pipe.

“The reality is that as far as municipalities are concerned it’s not exfiltration, it’s infiltration,” Reimer said. “It’s high groundwater pressures that ultimately may push past the gasket or push past the joint, which creates opportunities for infiltration and erosion of fine materials around the bedding. Municipalities have deep pipe applications and they’re concerned about gasket performance because of infiltration.”

Want to prove your joints can prevent infiltration? The Straub test is built for that.

The coupling is a flexible steel band with a rubber gasket that is attached around the joint after two pipes are gasketed and homed. The custom gasket has an entry port to introduce water and a secondary port to allow water to escape. Once installed, the gasket is filled with water and, after the pipes are restrained, the coupling is pressurized to place targeted stress on the joint. The pipe can then be inspected for any water leaking inside. 

The testing concept was born from Hamilton Kent’s acquisition of the Straub mechanical couplings business from Mississauga, Ontario-based Straub Tadco. An international company based in Switzerland, Straub manufactures high-quality repair couplings for all types of pipes. 

Isaque Nunes, a Technical Specialist at Hamilton Kent, said the test coupler is a natural extension of Straub’s core business.

“The Straub line is really a repair coupling,” he said. “If there’s a failure in a pipe, instead of having to disassemble the whole line and replace the pipe – which would be really costly – you can install a Straub repair coupling over the damaged pipe to make the repair.”

‘Ah Ha’ Moment

Adapting the Straub repair coupling to create a joint tester came from one of those “ah ha” moments in a meeting of the marketing team, led by Randy Reimer.

“One day we were all kind of brainstorming,” Nunes said, “and Randy said, ‘what if we were to develop something that could just go over the joint,’ and it was like the lightbulb went off for everybody around the table.” Heads were nodding, and everybody was thinking, “yeah, this could be huge,” Nunes said.

“It’s really a quick, innovative way to do a real-life application,” Nunes added. When it comes to deep buried pipe systems for stormwater and wastewater, municipalities are more concerned about water and grit infiltrating the system from the outside. “They don’t want to treat water that they don’t have to, so if a pipe is good, that means water is not allowed to get in,” Nunes said. “That’s essentially what we’re doing with the Straub test. We’re trying to force water into the joint – so it’s a real-life application of what the cities want.”

Several pipe and precast manufacturers have embraced the Straub test already, Nunes said. One of those producers is Precon, a diversified pipe and precast company based in the Northwest U.S. and Western Canada.

“Precon has jumped ahead and said, ‘we want to perform at a higher level than what the standard is,’ “ Nunes said. 

Cody Kibala, general manager of customers for Precon, confirmed that infiltration is the main concern among municipalities in his region, especially where deep-buried systems with large pipes are concerned. The exfiltration test typically is not possible with pipes over 900 mm (36 inches) in diameter. ASTM’s and Canadian Standards Association’s (CSA) protocols for joint testing don’t go beyond 900 mm, so Precon was interested in a test method for its large pipes, Kibala said.

“As your pipes get bigger, shouldn’t your diligence get higher?” Kibala said. “I think the onus on us as producers is that, as the pipes get bigger so should our responsibility. What Hamilton Kent has done with the Straub coupler has made testing more achievable for larger diameter pipe joints. The Straub test makes sure that the joint is performing and preventing leakage, so that a real benefit. It’s a great product.”

Higher Diligence

Precon demonstrated the Straub coupler during a plant tour hosted by the Canadian Concrete Pipe and Precast Association (CCPPA) in the spring of 2024. CCPPA promoted the plant tour to engineers and municipal employees in the Calgary region and provided transportation to the Precon plant. With the group looking on, the Precon crew installed the Hamilton Kent Deep Seal gasket on a 1050 mm (42-inch) pipe, homed the two test pipes and strapped on the Straub coupler.

A special restraining system fabricated by Precon was engaged to keep the pipes from separating as the coupler was pressurized. The coupler was tightened and water was pumped into the bladder. As the group looked on, the pipe joint was pressurized to 50 psi, well above the 15-psi standard for a C-76 pipe. “It was unbelievable,” Kibala said.

The HK Test Coupling by Straub simplifies joint testing and can eliminate time consuming, labor-intensive exfiltration testing in many cases, Reimer said. 

“If there’s one thing I know about concrete pipe and manhole plants, is that one of the things that the quality (QC) staff hate to do is hydrostatic testing. It’s tough, it’s difficult, it’s time consuming,” he said. Filling a large pipe with water, sealing the ends and pressurizing it is difficult and time consuming. The test may take the better part of a day to accomplish.

“With the Straub test, you don’t have to be concerned about all the water you would use to fill the pipe,” Reimer said. “You use only a very small amount of water to fill the gap around the outside of the joint. I don’t want to exaggerate, but it’s really revolutionary. It’s robust. It can be used over and over. It can be used on a jobsite. It can be used anywhere to test the performance of a joint.”

The Straub test is one of many innovations brought to the market by Hamilton Kent over the years, but Reimer would refer to it a little differently, and that’s where HK is in sync with producers like Precon.

“We’re working at trying to help the industry get better,” Reimer said. 

Cody Kibala echoed that sentiment. “They’re doing the right thing,” he said. “They’re making a better joint, a better gasket. That’s what we want too. We want to make things better for our customers – both for contractors and end users like the city of Calgary. So we’re very much aligned with Hamilton Kent that way. We just want to make things better.”