I have been installing Delta faucets with the built in grey plastic "custom fit" supplies for a number of years - lately these have been included in even high end models- and I considered them to be sufficiently reliable and even @#$%& proof. Due to a pump control problem my install in a 6 bathroom home was tested today with +150 p.s.i. ranges and I received a call back only for failures in these supplies (luckily someone was home). I believe there would have been no issues if a braided compression supply had been used.

Within hours, I was called to flood in a basement apartment for the same reason. The grey plastic pipe in both cases had slipped passed the ferrule and caused the joint to fail, but this time it was working under normal 50 p.s.i. pressure regulated conditions. It appeared manufacturers instructions were followed on these two joints.

Anybody with similar issues?

Did you use the factory connection, (I always do), or did you cut them to fit and used the supplied ferrules?

When it involves PEX supplies and plastic ferrules, I always tighten the compression nut as tight as I can to lock the ferrule to the supply. No failures yet.

Agree with HJ, I never cut the factory ends off delta supply tubes, they will bend or coil out of the way easily. Never had a problem. I did have problem using plastic ferrules on cut pvc tubes once in that although the threads on the new compression nut were clean, the threads on the stop were 'slightly" different and had some mineral build-up, making the nut hard to tighten. I tightened the nut using a hold-back wrench to the point I felt it was "tight" but it wasn't enough to compress the ferrule properly. You can guess what happened next. I refuse to use them anymore.

Do you add plastic stiffeners into the PEX tubing?

They use whatever Delta sends with the faucet, and I do not remember if they supply stiffeners, because as I stated, I NEVER cut the factory ends off so I don't use them.

some of those tubes that extend down from the faucet are sooo long you could have the sink on the second floor and the supply stops in the basement.

I never cut them either.I just use small zip ties and roll them hi and tie...

And they ALL curl up to fit the space needed.

I thank my Creator daily that I am retired and not compelled to install the junk the customer demands today.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638