TWO failed compression couplings

First post. Good site.

At a local facility, the water company in the area was installing a new water main near the centerline of the street adjacent to a school. Shortly after the construction was complete… the compression coupling at the point where the service line (2" plastic) meets the metal piping inside the facility failed. Water damage ensued… the coupling was repaired, however a couple days later, the compression coupling at the valve in the sidewalk also failed and needed repairs. Water was bubbling out of the sidewalk.

My question is what is the likely cause of these compression coupling failures? The service line and couplings were installed approximately 7 years before this incident and were functioning properly. I have an idea what may have caused the failure, but would like to here your thoughts first.

I appreciate any and all feedback.


N E E D M O R E I N F O.
What kind of plastic?
Was it really compression underground?

Obviously a manufacturing defect. Someone should file a class action lawsuit. :stuck_out_tongue:

Second the motion for more info. What plastic; even a color picture would help? Where are you (geographic location)? Need a picture of the 2" coupling; sounds like it’s inside the school? Picture is indeed worth 1000 words in a case like this. 7 years is probably too young to be worring about PolyB, but sounds like something that should be rather obvious with enough info to work with.

Sorry for getting back so late on this one. I have a picture of the repaired area where the failure occurred. I’ll try and post it.

The photos are, of course, of the coupling inside the building that failed. One close up, and one overall photo.



That is Polyethylene pipe, if they installed a new water main, it probably increased the water pressure causing the connection to fail.

It could be there was no “metal insert” inside the pipe at the compression connection and the pipe pulled from the threaded connection with the extra water pressure needed to cause the failure.

Or the fitting might not of been tightened correctly when it was first installed, but the lack of a metal insert at the pipe end compression connection is usually what I have seen cause the failure.

This is usually what I see as well. If the fittings worked fine for a 7 year period, chances are when the section was reassembled they were not installed properly. It doesn’t take much for them to fail if they are not seated correctly. Especially a 2" line.

How many times too, have you seen them try to use the old compression rings only to have them leak profusely either immediately or shortly after the truck leaves the driveway. It never works. You just have to use new stuff every time, even with the small crap under the kitchen sink.

What they said. Looking at the fitting, I don’t see any deep wrench marks. Anytime I ever put a 24 or 36" pipe wrench on a brass fitting it left deep marks. Plastic or no the thing has to be tight.