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Why Not CPVC for hydronics?

Starch Member Posts: 102
...oxygen diffusion?

I've seen cpvc get brittle after a few years, also don't know how it would stand up to the physical demands that a hydronic system could impose.

I don't think I would be comfortable using it. JMHO



  • heretic
    heretic Member Posts: 159
    Why not CPVC?

    Recently, I saw a fellow post a picture from China with a CI rad supplied by a PVC pipe. I thought; "Hey, that's only rated for 140 degrees".

    Well, some heating applications will never see 140 degrees, but perhaps a bit too close to the margin...

    But wait! What about CPVC? Roughly 100-200 PSI @ 180degrees, depending upon size. Most water systems run at 15psi max.

    Seems this is just not done, but why not?
  • heretic
    heretic Member Posts: 159
    Perhaps that's it

    o2 or longevity.

    Please understand I am not about to run out and do this.
    I just like to know the whys and wherefores of things in this universe.
  • Dale
    Dale Member Posts: 1,317

    I think how water boilers we think of as low temp are really rated up to 240 degrees, a push for even cpvc, the other issue is joint strength and expansion, with a 40 to 180 degree range the cpvc would be under alot of stress, and not alll brands of fitting and pipe give strong joints if mixed, the ASTM size alllows alot of range.
  • Steve Ebels
    Steve Ebels Member Posts: 904
    I was told

    At a hardware show years ago that

    A: it was never tested and therefore approved for long term high temp use.

    B: Genova (the company whose rep I was talking to) didn't want it to be reated for those types of uses due to liablilty.

    C: There were issues with longevity at sustained high temps.

    I would have to say my experience has born their conserns out. When CPVC became widely used a all of the farmers around here started using it for their dairy operations. In many cases they came back with failed joints after only a few years. These were invariably on the hot water lines which run 170*+ in a dairy for sanitation reasons.
  • Duane
    Duane Member Posts: 17
    CPVC not

    As a plastics engineer I can certainly recommend against using CPVC for applications above the rated temperatures. It may hold up in the short-term, but long-term stresses will cause the pipes to sag and bulge, and continuous heat will cause failure of the stabilizer in the PVC, leading to what is called "long-term heat age failure". That means busted pipes.

    I once managed a lab where CPVC was installed for cooling process machinery. The water "never" was supposed to get above 140F. It did sometimes, and the result was pipes that would burst under pressure with no warning. Seeing a 3" line go off is quite a spectacle.
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