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pex and freezing

steve gates
steve gates Member Posts: 329
How many times can pex freeze before bursting? At what temp will it only take once? Will it just expand and contract forever without damaged? Does it get significantly weaker?

I'm not asking about in slab but under a floor for example. As in an other plumber told me it won't. I kept my mouth shut. I did however note the attitude. With a water test on would the cooper shower riser split before the pex or would the pex expand enough to protect it?

Just never thought of risking it before nor will I.

I've seen pap in a floor freeze, bad. I've seen the results from a "test" under the floor(my nephew did that one). But pex's are different?

Thanks in advance


  • Weezbo
    Weezbo Member Posts: 6,232
    Howdy steve...

    pex is a fairly durabale product.will it freeze ?yup. can it freeze and not break ? yup. will it expand and contract with varying temps? oH Yeah ! :) is it invunderable ? nope. how hany times can it freeze and not break? well, heres a small experiment i did with it, i pumped up a piece of Rehau and a piece of Wirsbo capped them and added water and threw them out in 60 below for a while, days....then i took them and pounded them with a sledge hammer ...i am realatively secure in saying that a piece of copper would never have been able to withstand that! :)my buddy did about the same...he capped and filled the tube put it in the freezer,took it out after a few days took it outside and thrashed it on the ground to see if it would shatter, bought it back in and put it in his bench vise and started trying to bend it back and forth till it broke...he told me he was doing that and i told him that i found the stuff to be like a pacifier for hyped up kids...just give them a piece and see how long it takes them to break a piece in half :)it will keep them quiet and occupied for quite a while ...as it is a fairly tireing challange :) while you or i could snap a piece of 1/2" copper in a flash a piece of pex a is gonna be taking a while....another thing ,i pounded a 16 d sinker thru some pex let my buddy watch, warmed it with a heat gun pumped water tru it and then handed it back to him...Wheres the hole i put in it with the nail? he dont know cant see it..try that with a piece of copper :)
  • steve gates
    steve gates Member Posts: 329

    -60. That's dedication! to testing.

  • S Ebels
    S Ebels Member Posts: 2,322

    We had some 1" FoSta pex run in an attic that due to several wierd circumstances froze up solid. Like about 70' in length, stiff as a board. Drew went up there with a heat gun and after about 2 hours of thawing we got it flowing again. The whole 70' was solid and did not break or split. Copper would have failed without a doubt. I have a hunch that regular pex would be even more resistant to freeze damage than the PAP type products like FoSta pex due to greater flexibility.
    About the only things I've found that will damage pex is a nail or too much sun. It is tough beyond belief.
  • Weezbo
    Weezbo Member Posts: 6,232
    noi ...vis :) post button :)

  • Weezbo
    Weezbo Member Posts: 6,232
    Scott, in severe cold depending on where the pex is frozen

    a guy can take boiling water pour it right on the pipe and use the water like we use a heat gun or ...take a wash cloth and heavy towel use the wash cloth like a heat blanket and the towel to catch the water leaking..its pretty quick way to make pex go...
  • CLC
    CLC Member Posts: 4

    I've heard plumbers make similar statements regarding the nail in pex - heat it up fix. Will a punctured piece of pex actually seal itself up with applied heat enough to withstand its rating of around 100 psi/180F? I'm not sure I'd trust it in a joist bay above a finished ceiling.
  • DIYPeter
    DIYPeter Member Posts: 15
    PEX will freeze

    Had an instance where Kitec froze at about -10F, and burst. So did the copper feeding it. Was supply for a washing machine turned unintentional icemaker;-) Peter
  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    Sorry to dispell this myth but...

    We had a pex failure(Fostapex no less) this winter. Seems the contractor left an opening to the wind and weather in a chase that we ran pex through.(wind chill about -15°F) The pipe froze hard, and the wind was hitting right on a tee.

    My theory about the leak that ensued is....The pex expanded, as it is prone to do,(Not Split!) but ALSO expanded the press fitting in the same spot as the freeze happened.When the thawing occured, the fit was weakened and the pressure of the water main was pushing against the freeze plug ahead of it in the line, causing the pipe to pull away from the fitting.

    Water expands in both extremes, and I can't think of any other cause for the failure. The press tool was tested, and found to be within tolerances accepted as "proper". I don't know what the testing criteria is, but I'm quite sure the reson for the failure is what I stated. Hydronics INDEED!. Chris
  • hr
    hr Member Posts: 6,106

    of course the split happened as you thawed, not during the freeze :) Correct?

    I've seen old PB freeze and swell up like a sausage and not burst. i think it depends on how much freezes, how long it is frozen, and what kind of expansion room there is. I don't believe there is a simple one answer to this question. Depends too much on multiple conditions.

    Not all copper splits when it freezes, just depends. I've thawed tons of soft type K main lines in Utah. Can't remember any breaks. It would usually push off fittings before it split. Just don't try to put a new fitting on. it usually expended enough to prevent this. Same with hard drawn copper that doesn't split. Repair couplings seldom fit.

    hot rod

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  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    Hot Rod,

    NO SPLIT !!

    The press RING was pushed away from the "press position"while freezing , and during the thaw, it seperated from the fitting due to pressure/displacement during the thaw cycle.(It expanded during the freeze)

    We have high pressure in most homes here, until a PRV is put on the main.

    In my estimation, the Fostapex thawed BEFORE the freeze in front ( rest of the system side) did, and the pex came off of the fitting. Hope this makes sense. I can't think of any other way to explain it. Chris
  • Mike Thomas
    Mike Thomas Member Posts: 1
    Pex and Freezing

    I used to do a lot of pex in Alaska. Had a three bedroom house I had just finished. The homeowner left for Hawaii for two weeks, heat went out and the place was frozen solid at -40 for two weeks. He called me when he got back. I went over, changed the Manabloc manifold and got him going. Not one pipe was broken. I was in and out in less than 45 minutes. I was convinced that if there was some sort of pressure relief valve on the manifold, even it wouldn't have broken.
  • Tom_35
    Tom_35 Member Posts: 265
    Frozen Pex

    I made a post 5-6 weeks ago about a job where we had several joints in a concrete slabl freeze.

    The house was under construction and open to the wind. The weather here has been mild this winter (very few days in the teens, and mostly in the low 30's; I know, below 32 is freezing). What was crazy about it was none of the copper manifolds burst.

    The finished floor level was anywhere from 6" to 5' above the ground outside. The only thing we can figure is that the InsulTarp did nothing for the insulation values. I've read plenty of info on the Wall since the slab was poured about the questions on InsulTarp and won't be using it again, but still don't know if that was the problem. This is the only job we've ever had where anything froze and we've had much colder winters in the past.

    Tom A
  • Weezbo
    Weezbo Member Posts: 6,232

    a couple winters ago ,my buddy had piped a place and the hrv ladds outdoor supply air found itself the only path it could make right along the aquasafe! well...it no likey 50 below :)the GC gave me a call and said the water no mojo so i went to see if i can help my buddy out...after fiinding the frozen pipe in the crawl space i went and drug in my weed burner:) not some pathetic 35000 btu buh my extra fine 85000 4" copper fitting weed burner:) that does a respectable job of heating small sewage treatment plants :)so not wanting to mees anything up i start in the furthest corner of thecrawl space4' 8"ish and crank up the heat and gradually work my way back to theopen crawl speace accesswhere thepipe was frozen...by the time i got there it was like 90 in the shade and whatever could have been frozen was now begging for any kind of relife from the heat :)) you do not have to direct heat at cold ...it knows how to get there :) then after turning off my weed burner i pointed out the minor oversight to my GC buddy and he insulated the tubing and opened some air around the duct work and the tubing...it never froze again :) i do not advocate putting nails or screws in pex it was only something that suprized my friend enough that he at least decided it was a good idea of his to use the stuff in the future :);)
  • hooflungdung
    hooflungdung Member Posts: 1
    PEX and freezing

    Currently living in a nice home which I don't own in a ski resort town.  There is a utility room off the garage but no water would flow from the sink last weekend.  I opened the faucet a little and late in the afternoon it thawed and water would flow.  Both cold and hot sides froze.

    This house was completed 7 or 8 years ago.  It has Wirsbo Aquaplex tubing.  The owner says he has never noticed the pipes to this sink freezing before (he is here most of the winter).  Strange but the sink doesn't get used much.   I believe the conditions have been relatively constant over the years.  It has frozen for the past 3 nights but if I open the faucet it thaws in the afternoon (I have also been playing with the garage thermostat). Potentially this tubing has seen hundreds of freeze/thaw cycles!  It's possible it has stayed frozen for most of the winter, but it certainly has seen freeze/thaw cycles during spring and fall.  So I'm guessing it has seen at least 100 cycles and likely many more.

    I am a materials engineer and this amazes me!  But I think we had better fix the problem because eventually that tubing will break.  In the short term I will let the faucet drip.
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