Sharkbite physics

[.Nolan.]

I'm going to be replacing my leaking water main valve, and I'd like to use a sharkbite fitting. I notice the slip joint ball valves (part# 24735LF) do not have the interior white nylon collar (see first picture) that the straight ball valve does (part # 22222-0000LF). What is the purpose of the nylon collars? Don't these collars restrict flow because they decrease the interior diameter of the pipe? And since the nylon collars don't fit flush against the interior of a copper pipe (they seem to flop around inside copper pipe - see second picture), doesn't this lead to more turbulent flow at the entrance to the valve? I'm wondering if I would get better water flow through the slip joint because the interior diameter is wider and the path straighter without that nylon collar? Or does it really not make a difference?

 

[Reach4]

The slip fittings are a special thing for filling a gap.

See https://www.pexuniverse.com/leaks-sharkbite-and-other-brands-push-fittings-and-how-prevent-them where it says

When/if removing a PEX stiffener (insert) from the push fitting – do it properly. Hold the insert with needle-nose pliers and push on the lip of the fitting with a disconnect tool (in the same manner a pipe is disconnected), while slowly but firmly pulling the insert out.

 

[Sponsor]

 

[Jadnashua]

That fitting is REQUIRED when using on pex. It is an internal stiffener. If you're using copper, you can take it out and throw it away. It keeps the end of the pipe round and stiff so that the external seal can work right and the locking ring can work properly.

It's the same idea as the internal stiffener when using a compression fitting with pex. The same valve will work on both copper, cpvc, and pex, but is required on the pex for the same reason.

The reason why it's loose on copper is that the ID of copper is larger. It's a much snugger fit when using pex that has a thicker sidewall.