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user-471779 | Posted in General Questions on

I am obsessing over which pex to use for a whole house manifold installation. The choices are pex-a (uponor) vs pex b (viega).

Uponor seems easier to work with, less kinking, better flow etc.

What I am most concerned with is:

1.longevity (this is my forever house)
2. safety (leaching of chemicals into drinking water)

I am on a well.

Any input as to the longevity and safety of these two different types of pipes?


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  1. GBA Editor
    Martin Holladay | | #1

    Here is a link to an article that explains the difference between PEX A and PEX B:
    Types of PEX tubing.

    Here is a link to a GBA article on PEX safety: How Safe is PEX Tubing?

  2. user-471779 | | #2

    Thank you Martin for the links..
    I was hoping someone would just tell me which one to use!!! I am so burnt out on making decisions!! maybe I should just flip a coin...

  3. GBA Editor
    Martin Holladay | | #3

    Ah, yes -- the burdens of adulthood.

  4. user-2890856 | | #4

    PexA is produced with a better manufacturing process than PexB as the crosslinking takes place during the extrusion process . PexA products usually achieve an 85% crosslinking while PexB products average a 65-70% .
    One point in the article or discussion Martin linked to is a bit inaccurate . Pex has not been available here since the 80s but was available as early as the mid 70s . It is more resistant to chemicals commonly found in plumbing and heating systems than what it has replaced . Uponor currently holds an un official world record for long term testing at elevated temp and pressure , Tests at Studvik in Sweden subjected the tubing to 203*F @ 175 PSI from 1973 through 2009 . There is not another manufacturer that can make that claim .

    PexA fitting systems are also much stronger , less restrictive . Uponor's fitting systems , in particular the cold expansion method is by far the best fitting system there is , pipe always tightening onto fitting as opposed to many other systems where pipe is pushing out against the restraint .

    You can use other brands of PexA also with Uponors fittings , like Mr Pex .

    Don't flip a coin , use the PexA and use Uponor or Mr Pex tubing .

    1. cldlhd | | #22

      I was planning on going with pex A for the reasons you listed my only concerns are I have fairly high water pressure, between 80 and 100 PSI, and a decently high level of chlorine. I have read that PEX A is less resistant to chlorine than PEX B and that and exposed to chlorinated water at higher temperatures ( I keep my HPWH set to between 125 to 130°) It will have a significantly lower bursting pressure than PEX B. Is this still the case? I've also read that it is more likely to leach off chemicals. If it wasn't for those two issues I would go through the extra cost and hassle of getting PEX A because of the connection methods, it isn't available at the local big box stores like PEX B either . I realize this is an old thread but I figured it's still a current conversation and maybe manufacturing methods have changed? Thanks

  5. user-471779 | | #5

    Wow Richard thank you!!!! And asked question now is... are u familiar with the manabloc manifold... If so, they only offer compression connection and a crimp... Can I crimp uponor pex a... Or should I use their compression option?

  6. iLikeDirt | | #6

    PEX in a "forever house" (any house IMHO) should be downstream of a water filtration system that removes chlorine. The reason is that chlorine eventually oxidizes and embrittles the pipe over time as the sacrificial anti-oxidizing agents are, well, sacrificed. With no chlorine in the water, this risk disappears. You also want high-quality low-zinc fittings. Don't cheap out.

    1. cldlhd | | #23

      But you didn't offer what you think should be used? Currently the vast majority of my house is plumbed with copper. I do have one area I was planning on replumbing, it's accessible behind a panel, and was contemplating using either PEX A or PEX b. You read so much about every different method have an issues, copper can develop pinhole leaks etc, cpvc is supposedly better handling chlorinated water but then you read a million articles about how it gets brittle. I would contemplate installing a filter that would take out the chlorine but the purpose of the chlorine is to keep bacteria down and having All my pipes full of unclorinated water seems like that could be a health risk.

  7. charlie_sullivan | | #7

    If you opt to flip a coin, here's a table of the characteristics of different US coins.
    As occasionally happens, the lowest cost option, a penny, is probably also the coin with the lowest environmental footprint.

    More seriously, I'll put in a vote for PEX-B. I got my kitchen sink changed over from lead-soldered copper to Uponor PEX-a about a year and a half ago, and I found taste terrible in the first few months--a strong plastic taste. I still flush the pipe before drawing a gallon of drinking water to save in a pitcher, even though I probably don't need to. I haven't done a controlled comparison to PEX-B, but given the comparison Martin linked to, I'd expect it to be significantly better in that regard.

  8. user-471779 | | #8

    The water is actually from a well, so chlorine shouldn't be a problem.... This whole thing has driven me a little crazy but I flipped the coin.. Pex A won.. It's been ordered..... ( but if I had seen Charlie's post earlier I probably would have ordered Pex B...... uggh....) Hopefully That taste thing doesn't last!!!

  9. user-2890856 | | #9

    You cannot crimp Uponor pex . A few years ago I was called to a group of modular homes to determine why the Uponor piping was leaking . Long story short , it was not the tubing leaking but the manufacturer of the home thought it would be OK to save on some fittings and used crimp rings and fittings made for other pipe which are much smaller in diameter . Pex always wants to get back to it's original size and form (memory) . If you use other than Uponor fittings and crimp it , it WILL LEAK , and there will be no warranty for you .

    If you intend to use the Manabloc make damn sure the threads for the Uponor compression fittings are compatible .

    As mentioned before in another post , for Charlie

    Pex A 85% average crosslinking

    Pex B 65-70% average crosslinking

    Pex C 70-75% crosslinking

    There is a clear winner here and showing is Pex B

    My advice is to use the Uponor EP valved manifold

  10. charlie_sullivan | | #10

    Richard, thanks for the compatibility warning. Was that by any chance the system in this lawsuit?

    That's brass fittings with stainless clamps.

    The uponor technical manual says you can use standard crimp fittings with their tubing, but warns against:
    A. Others' expansion fittings with uponor pex, or
    B. Uponor fittings with PEX B.

    That points to maybe brass fittings with copper crimp rings being OK with pex-a, but not if that's what Richard saw failing in the field. So Richard, was that failure with stainless rings or copper rings?

  11. Expert Member
    MALCOLM TAYLOR | | #11

    I think you mistyped your last response suggesting using Pex B, while your argument favours Pex A.

  12. user-2890856 | | #12

    Definitions ; Uponor receives calls all the time from plumbers who become argumentative about why they cannot use the crimp rings , ss or copper that are in their truck with uponor tubing . Those folks are always told that you CAN use them but there will be no warranty coverage . What does that tell you ? It clearly tells me that you cannot do it and expect any sort of system integrity . Uponor does not make a crimp ring fitting nor will a crimp ring fit over Uponor tubing when a Uponor fitting is used . There is the catch , you'll have to really break your proverbial balls to use it the wrong way and then you will have no defense and Uponor is not in an actionable position .. Ignorance is reparable , stupid is forever .

    I have attached the latest Uponor Technical Manula and was wondering if you could point out where in that document taht it states you can use a crimp ring ?

    Uponor produces for sale , compression fittings , press fittings and cold expansion fitting . The use of anything other than these will void any and all warranty claims .

    Others fittings will slide right into Uponors tubing and every tubing , this is the problem . You cannot put a Uponor expansion fitting into the tubing without first expanding the tubing with an expansion ring (required) around the outside of the tubing also . A compression fitting is a compression fitting as all are similar and Uponor's press fitting begins as a tight fit between the inner tube wall and the outer diameter of the Uponor press fitting .

    Uponor's fittings with PexB is quite entertaining . One would have to expand the PexB and you can , but the tubing will probably eventually leak because the molecular linking is of such a low percentage and again , why would one do it .

    Others fittings with Uponor or another PexA is yet another interesting situation in that the fittings are smaller in OD than the ID of PexA , B , C . The fact that Pex B and C use a crimp shows their inferiority since they are warranted to not leak all the while the product should be attempting to reach it's original dimension . Remember , this tubing has memory . Turns out that PexB and C have less memory apparently since they are willing to stay in the constrained size whereas the Pexa products will push out against the crimp ring whether SS or copper and a leak path will form every time .

    You can do anything you want but must be willing to accept the consequences . I happen to be one of those funny guys that will not put anything in anothers home that I would not have in mine . At the end of the day PexA products and fiitings using a cold expansion type fitting system will forever be getting tighter to the fitting and all others will be trying to loosen . You make your own decision . Should not be that difficult either since the price difference is not that great to expose yourself to that big a loss .

  13. user-2890856 | | #13

    No mistake Malcolm . The clear winner is PexA while PexB is the clear third choice . Win , place , show . Maybe the horse racing reference was the problem .

  14. Expert Member
    MALCOLM TAYLOR | | #14

    Sorry Richard - I didn't get the implications of "and showing" in your post:

    "There is a clear winner here and showing is Pex B"

    I've got it now.

  15. rocket190 | | #15

    Richard, I agree that the Upunor fitting system seems to be superior, but it's my belief that it has more to do with unrestricted flow rate. Whereas barb fittings are placed inside the tubing, the already smaller ID of pex (compared to copper) becomes even smaller with these fittings. As you know, the Uponor expansion fittings are full flow. However, by your logic, wouldn't the pex-a, which was expanded over the barb fitting, want to return to its original size and therefore tighten itself onto the barbed fitting in the same manner it would on an expanded fitting?

    I've used a lot of pex-a with stainless cinch clamps on barbed fittings and I've never had one leak. I've hydro tested these to 200 psi with no issues. Also, many people use the same combination for compressed air, which is even harder to seal, with no issues. Please explain.

  16. user-2890856 | | #16

    Crimp fittings is a very general term . There are PexA manufacturers that use a barbed fitting with a crimp ring . Those fittings may be very different in size than a Viega or Zurn fitting . I imagine the fittings you have used with crimp rings are manufacturer specific or at least share like ASTM numbers among all the other standards . At the end of the day we must be cautious what we tell folks it is alright to do . The other side of the coin is that we allow manufacturers a way out of warranty claims should they arise .

    You will have to excuse me , when you say a barbed fitting the first thing that enters my mind is a cheap big box store , thin walled brass fitting that is nowhere near what one would consider a good fit , this fitting will leak every time when using Uponor tubing . Maybe more specific fitting references would avoid confusion .

    Just like with anything else , operators can cause problems . Uponor's system allows me to visually determine if a joint is made right and address it and the guy who made that joint . You hold the pipe and the fitting in different hands and push them together after you have expanded the tubing . Your hands cannot be on the pipe and fitting and operating a crimp tool all at once , physically impossible . Furthermore , Most who state they have never had a leak on anything have either not done enough of it or are mis stating the truth .

    Whose tubing and fittings do you employ Rick ?

  17. rocket190 | | #17

    Richard, I have to call BS on your response. Personally, I've used mostly Nibco brass fittings and I use only Uponor tubing. I haven't had any leaks. That being said, I haven't seen a rough in my area with anything other than pex-a and barbed fittings and stainless cinch clamps in a few years. It's what almost all plumbers have gravitated towards in residential installs. In some commercial applications I still see expansion style fittings used or Propress.

    I still agree with you that expansion fittings are likely superior, but to say that cinch clamps will certainly leak is a gross exaggeration. There are millions of these connections in place that are not leaking.

  18. Expert Member
    MALCOLM TAYLOR | | #18

    For at least a decade almost every building in British Columbia has been plumbed with pex and crimp rings. I've plumbed a half dozen that way myself and have never had a leak.

  19. user-2890856 | | #19

    Rick ,

    You can call BS if you'd like . Opinions are like assholes ya know . I myself use systems that will , should there be a problem , have the manufacturer not wriggling out of a warranty claim . If you choose to use that type fitting with Uponor tubing , be my guest , in the event of an issue you will however find yourself on an island with no support from the manufacturer . Hope you have very good insurance or at a minimum , a claim adjuster who cannot read .

    Every time I have seen Uponor tubing used with a sloppy first fit brass fitting they were leaking . That's why I saw them because if they were not leaking I would not have been called , I must be lying since you called BS , I guess . I will ad that every one of those jobs looked like a kindergardener did it but the pex was cut square and not all the joints were inserted far enough .

    Feel free to make your own rules and do what you wish and good luck to you with your endeavors . Maybe if you ever have one of those failures someone won't look you up on the internet and see this discussion , that would kinda suck for you .

    I must ask why you use the Nibco fitting instead of one the manufacturer distributes ? Did you just not want to make the investment in tooling ? Is the Uponor system too expensive ?

  20. user-1041981 | | #20

    Dean, one thing to consider that I did include recently in my forever home - Uponor integrated fire sprinkler system. I wanted to know that I had done what I could to keep my family safe and not kick myself for a Stamford, CT type of situation:


    Uponor will engineer/design the system for a fairly low fee. See:
    The design will be in accordance with NFPA 13D:
    You can't just "wing it" since the placement of the sprinklers has to take into account obstructions (like walls, chandeliers/fans) and other sprinklers (if too close, they will cool neighboring sprinklers and delay or prevent their operation).

  21. zurn | | #21

    Water pressure control valve ZW209 provides steady downstream pressure and allows high flow rates. Standard features ease maintenance and repair, delivering the lowest total cost of ownership.

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