Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

PEX Fittings: Which Type Is the Most Freeze Tolerant?

Tom_22
Tom_22 Member Posts: 108
It's well known that PEX pipe is better than most (all?) rigid for ability to tolerate freezing without failure; but I haven't heard much about which fittings offer the best freeze tolerance.

Is brass or plastic better? And if plastic, is there a preference between the types? Apparently, there are several different types of plastic.

The application is a vented, uninsulated crawlspace high atop a Pocono Mountain in Northeastern Pennsylvania.


I realize ideally one would eliminate the use of fittings altogether in the crawlspace, but this is a retrofit of a previously foreclosed upon property, and some hookups will be to existing copper pipes stubbing through the first floor into the crawlspace. The crawlspace main is missing. Apparently, stealing copper pipe from empty homes and scrapping it is a popular activity around the Poconos.

Comments

  • SWEI
    SWEI Member Posts: 7,356
    edited December 2015
    PEX pipe will survive a certain amount of freezing, but regular freeze-thaw cycles will bulge it beyond hope. PEX-a is a bit tougher that the rest.

    No PEX fittings that I am aware of are truly freeze resistant. They must be made out of very rigid material in order to seal to the pipe. You freeze them, they explode.

    Aquatherm (thermally welded coextruded polypropylene) tolerates a bit more freeze-thaw than PEX does, and the fittings are made out of the same resin as the pipe. I still wouldn't spec it for that kind of location without a heat trace tape or some kind of water temp control/safety system.
  • Jamie Hall
    Jamie Hall Member Posts: 20,477
    or glycol... much as I know that it's a pain in the ... neck.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Tom_22
    Tom_22 Member Posts: 108
    I'm not planning on letting the PEX piping and fittings freeze. I will insulate it, and close the crawlspace vents, and I may heat trace it if I can get an idea from any locals if they recommend it for those conditions around there.

    I was just wondering if it did freeze, despite whatever reasonable steps I take to prevent it, if there was a marked preference for brass or plastic.

    Asking around a little bit since I posed the question here, I got a couple of opinions that if anything, plastic was preferable to brass for freeze resistance.
  • hot_rod
    hot_rod Member Posts: 18,227
    The copper pex fittings would be the softest and most freeze tolerant, probably. Sioux Chief and others offer them.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,785
    Hello: NREL did some freeze testing of PEX with brass and plastic fittings. The plastic held up better as it lost heat at around the same rate as the pipe. With brass fittings, they freeze quickly, trapping freezing water in the pipe, forcing a burst. Damage happened in pipe that was pretty short, between fittings. Hope that helps!

    Yours, Larry
    kwalshMaxMercyPC7060
  • kcopp
    kcopp Member Posts: 4,092
    edited December 2015
    From my experience I have never seen a fitting freeze failure on pex due to freezing. I have see a fair share of splits on pex tubing from PexA to pexC. The pex A tended to fail right next to the fitting where the B&C tended to fail further away.
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    One would hope the nearby pex would take up the expansion, I guess all bets are off if that one fitting is extremely exposed
    MaxMercy
  • ChrisJ
    ChrisJ Member Posts: 13,898
    edited December 2015
    Regarding the pex taking up the expansion, I thought only pex a claimed this? I've never seen pex b or c claim they tolerated freezing.

    Speaking as an amateur, pex a with the expansion tool is the only pex I'd consider using in my home.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Dave H_2
    Dave H_2 Member Posts: 520
    The fittings are not the weak point in a freeze situation. The tubing is going to be the weak point. Not that I am saying the pex is weak by no means.
    My suggestion is to go with what is most common and what you can get on the shelves at the local wholesaler.

    Dave H.
    Dave H
  • kcopp
    kcopp Member Posts: 4,092
    The best tubing I ever saw for freeze tolerance was actually Poly Butylene. I saw an entire house freeze up one January and the only breaks were on a the heating system... the water was 100 w/ the exception of the shower valve drop ear 90 that popped off the riser.
  • hot_rod
    hot_rod Member Posts: 18,227
    Tube expands a lot, the next fail point is the fittings squirt off the tube, same with SharkBites in a hard freeze. Fittings breaking are the last failure typically
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MaxMercy
    MaxMercy Member Posts: 336
    Tom_22 said:

    I'm not planning on letting the PEX piping and fittings freeze. I will insulate it, and close the crawlspace vents, and I may heat trace it if I can get an idea from any locals if they recommend it for those conditions around there.

    When insulating any pipe, leave the side open to the area less likely to freeze - so if in a crawlspace, insulate beneath the pipe and leave the top exposed to the living area (less likely to freeze or at least freeze last).

  • Larry Weingarten
    Larry Weingarten Member Posts: 2,785
    Hi @kwalsh , J Burch did a number of reports on freezing pipe before he retired. We're both taking info and different perspectives from the same author. In the report I was looking at seven years ago, he was looking at how freezing was initiated and how it progressed. As HR says, it was tubing that failed. I don't think we have much, if anything to disagree about. We're just checking out different parts of the elephant.

    Yours, Larry
    PC7060
  • hot_rod
    hot_rod Member Posts: 18,227

    Hi @kwalsh , J Burch did a number of reports on freezing pipe before he retired. We're both taking info and different perspectives from the same author. In the report I was looking at seven years ago, he was looking at how freezing was initiated and how it progressed. As HR says, it was tubing that failed. I don't think we have much, if anything to disagree about. We're just checking out different parts of the elephant.

    Yours, Larry

    I think all the Pex manufacturers have done fail tests with both air pressure and freezing the assemblies.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream