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PEX Fittings: Which Type Is the Most Freeze Tolerant?

Tom_22Tom_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.


  • SWEISWEI 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 HallJamie Hall Member Posts: 13,482
    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.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Tom_22Tom_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_rodhot_rod Member Posts: 13,888
    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
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Member Posts: 1,919
    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
  • kcoppkcopp Member Posts: 3,538
    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_4Bob 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
  • ChrisJChrisJ Member Posts: 11,277
    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_2Dave H_2 Member Posts: 392
    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
  • kcoppkcopp Member Posts: 3,538
    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.
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