Hotel CPVC Expansion Joints

Summary: No sooner had I published the article on the double standard of CPVC pipe vs Copper pipe, a leak developed at one of my hotels with CPVC domestic water pipe.  Here is the story.

In my article “CPVC vs Copper in Hotels: Is there Still a Double Standard?” I shared my observation that the double standard for CPVC and Copper pipe was behind us with regard to pipe failures.  But within hours of publishing that article, I awoke to see the email trail of a hotel in Bellevue, Washington experiencing leaks in the piping.  Here is the story.

The mains of this 7 story hotel are a brand of CPVC called Coristan, which is a high grade of CPVC suited for larger diameter pipes.  As it turns out, there was no problem with the pipe.  However, we all know that CPVC has a higher coefficient of expansion than copper.  Thus, it is mandatory to use expansion joints to compensate for pipe expansion as the water in the pipe rises from 50 degrees to 120 degrees.  In a long hotel, this can be a significant expansion and without the expansion joints, the risers would be stressed and possibly sheared off.

What happened in this instance was a failure of the expansion joint.  Fortunately, the leak was small and the amount of water involved was limited.  Of course, even a small amount of water on ceiling tiles and carpet can cause significant monetary loss, but consider that other extreme of a 6 inch main water pipe flowing at full pressure.  That would be enough water to fill the hotel basement before someone could find the valve.  But, again, that is not what happened.

Below are pictures of the failed expansion joints.  Note the cracks in the bellows.  At one point it was thought that the flexing of the expansion joint had caused the failure, but the final analysis determined that the bellows failed from lengthwise stress caused by the water pressure, not the temperature fluctuations.   Be aware that there is a continuous stress on the pipes from the water pressure.  For a six inch pipe, the stress at 80 psi is about a ton of force.  It is less for smaller pipe diameters and is stricktly proportional to the area of the inside of the pipe cross section.

What was missing were extension limiting rods that keep the expansion joint from extending too far.   If you use this type of expansion joint, specify the joint expansion rods.




A more traditional means to control expansion is a “U-loop” as shown in the two photos below.  This is fool-proof, but requires extra space that may not be available.



Below is a response from the manufacturer regarding the failure mode of the bellows expansion joints in the previous photos.  You be the judge of whether this is an accurate assessment.

PROCO PRODUCTIONS, INC response to failure

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