Steve, you forgot to add:
- The design of the fittings is poor.
- The materials used in the construction of some of the fittings are substandard.
- The quality control of the manufacture of some of the fittings is substandard.
I recently built a house and was using sharkbite fittings. The first assemblies went just fine. Then I went back and bought a bunch more. The first two I assembled broke during assembly. Further investigation revealed that approximately 1/3 of the various fittings were either missing components, were broken, or some of the components weren't completely formed, ie; part of a "rim" on the component was missing.
I removed ALL of the sharkbite fittings from the job, went back to Lowes, and returned them all. Lowes said they have had a BUNCH of returns recently for defective fittings . . . .
Thank God I hadn't put everything together, turned on the water, and been away from the house . . . .
So the three failures I bulleted above are ALSO reasons that sharkbite fittings fail.
I replaced all the fasteners with the Pex Stainless steel crimped rings.
Personally, I'll not be using sharkbite fittings again, ever. YMMV