Dry fitting PEX install, why are some fittings loose, and some snug?

[Mike Rock]

I am re-doing my bathroom and starting to dry fit the PEX pipes. I am using the Apollo brand I purchased at HD.
I noticed as I was dry fitting everything with one length of pipe I was using, the fittings/elbows were easy to slip in and out of the PEX, to a point they were falling out of the PEX. I did not think much of it, I just said when I crimp, they will be fine.
Then as I started dry fitting with another new length of PEX, I noticed now the fittings were nice and snug, and did not fall out.
Is this a quality control issue with the loose PEX pipe?
Or is this normal for PEX pipes to have slight variations?

 

[Sarg]

Do you have a mix of PEX-A and PEX-B fittings ?
Or a mix of different piping - Apollo makes both and HD sells both the PEX- A and the PEX - B.

 

[Sponsor]

 

[Mike Rock]

Do you have a mix of PEX-A and PEX-B fittings ?
Or a mix of different piping - Apollo makes both and HD sells both the PEX- A and the PEX - B.

Nope both fittings and pipe are all the same ,type B

 

[Sarg]

Sounds like there was a length of the type "A" mixed in ...... beyond that another mystery.

 

[Reach4]

https://www.engineeringtoolbox.com/ASTM-F876-PEX-tube-d_2139.html

PEX has a specified outer diameter, and it has a minimum wall thickness. There is also a maximum, that is seldom referenced.

https://www.iapmo.org/media/5460/summary-of-changes-astm-f876-2015a-2017.pdf page 5 says

The minimum is the lowest wall thickness of the pipe at any cross section. The maximum permitted wall thickness, at any cross
section, is the minimum wall thickness plus the stated tolerance. All tolerances are on the plus side of the minimum requirement.​

Pages 4 and 5 show a tolerance for the outer diameter.

So there can be different IDs and still meet the size spec within the tolerances.

 

[Tuttles Revenge]

The only advice I have is that Dry Fitting water tubing will lead to surprises when you turn the water on and find fittings that haven't been crimped..

 

[Mike Rock]

https://www.engineeringtoolbox.com/ASTM-F876-PEX-tube-d_2139.html

PEX has a specified outer diameter, and it has a minimum wall thickness. There is also a maximum, that is seldom referenced.

https://www.iapmo.org/media/5460/summary-of-changes-astm-f876-2015a-2017.pdf page 5 says

The minimum is the lowest wall thickness of the pipe at any cross section. The maximum permitted wall thickness, at any cross
section, is the minimum wall thickness plus the stated tolerance. All tolerances are on the plus side of the minimum requirement.​

Pages 4 and 5 show a tolerance for the outer diameter.

So there can be different IDs and still meet the size spec within the tolerances.

Interesting, thanks. I had figured there would be some kind of tolerance. I was just concerned if I had gotten a bad pick from the pile, but when I crimped everything, it all seemed tight.
I also have a call in with Apollo tech support to confirm.

 

[Mike Rock]

The only advice I have is that Dry Fitting water tubing will lead to surprises when you turn the water on and find fittings that haven't been crimped..

Thanks, yes everything crimped, I has to dry fit first because I was working in a tight spot.

I have not completed all of the rough in yet, still have to replace a couple of valves in the basement, so I have not been able to turn on the water to test yet.