Pex A Versus Pex B

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wado66

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I have been looking at articles and videos on Pex A or Pex B for my bathroom reno.
It seems the general consensus that I have seen is using Pex A.
More flexible and less flow restriction.
Watching some of the tutorials on using the expansion tool and fitting install got me wondering.
If Pex A is this flexible/pliable it looks to me like hot and cold could affect this connection.
Being a DIY'er and not in the trade per say, it just looks concerning to me that there is no positive locking of these connections. Just expansion and contraction of the polyethylene material.
If I take a really hot shower, what keeps the Pex A from expanding around the fitting and leaking?

Another instance that happened that brought this thought in my head was,
I bought a new camper. It has Pex B with the metal crimps on the fittings.
The dealership said to check these fittings after 6 months and a year. Sure enough, right at the water heater I had a fitting leaking. So I put a hose clamp on it and so far so good.
I know its not the same as the Pex A concern, but leaks are leaks and it just got me thinging.
 

John Gayewski

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Pex A is, for all of time, trying to shrink back to the shape in which it was manufactured. The ring that holds the tube to the fitting is also trying to shrink to its original form. In pex B, the B doesn't stand for better, it stands for cheaper and coated in pex a.
 

JohnCT

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Many PEX B pipes are now certified for F1960 expansion fittings like the A type, so if you prefer the expansion connection (I do), then you can use either A or B. Just check your B supplier if you're going that way to make sure they certify F1960. Zurn and Sioux Chief do I believe.

John
 

John Gayewski

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Many PEX B pipes are now certified for F1960 expansion fittings like the A type, so if you prefer the expansion connection (I do), then you can use either A or B. Just check your B supplier if you're going that way to make sure they certify F1960. Zurn and Sioux Chief do I believe.

John
Are you sure about this?
 

JohnCT

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Are you sure about this?

Yes. I just double checked. Zurn certifies their PEX B for F1960 expansion.


As far as I can tell, Zurn only makes B because they describe it as being made by the silane method.

This was cut/pasted from Sioux Chief, who makes both A and B but certify the fitting systems as the same for either:

APPROVED FITTING SYSTEMS
PEX-B Tubing: ASTM F1807 / ASTM F2080 / ASTM F1960 / ASTM F2159

PEX-A Tubing: ASTM F1807 / ASTM F2080 / ASTM F1960 / ASTM F2159

John
 

John Gayewski

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Yes. I just double checked. Zurn certifies their PEX B for F1960 expansion.


As far as I can tell, Zurn only makes B because they describe it as being made by the silane method.

This was cut/pasted from Sioux Chief, who makes both A and B but certify the fitting systems as the same for either:

APPROVED FITTING SYSTEMS
PEX-B Tubing: ASTM F1807 / ASTM F2080 / ASTM F1960 / ASTM F2159

PEX-A Tubing: ASTM F1807 / ASTM F2080 / ASTM F1960 / ASTM F2159

John
I'm going to have to look into this. I'm not sure how it qualifies as pex B AND can be expanded. I'm not sure why they would not want a new label or trademarked name on such a thing. This must be what our local holt supplier was telling everyone about when they said they now carry expansion pex, but I've never seen pex a there.

I just watched a video on zurn's site about this they never call it pex B. They say they have a new resin formula and it's crosslinked. But they aren't very descriptive.
 

JohnCT

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I just watched a video on zurn's site about this they never call it pex B. They say they have a new resin formula and it's crosslinked. But they aren't very descriptive.

Right, they don't call it B but they don't call it A either. They say in the video that it's the same pipe and they also say it's made with the silane method which is by definition B. All PEX is supposed to be crosslinked as well, it's the just the percentage of crosslinking that determines whether it's A, B, or C as I understand it.

A few years ago I was screwing around and expanded some B and pressurized it and it held fine. I didn't leave it in service of course but I was curious.

John
 

GrumpyPlumber

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IMO, Pex B is near useless for the contracted ID at the barbs.

You cannot use them on shower valves, I've had countless service calls for slow flow and shower heads backflowing with the tub open.
 
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