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Thread: Will PVC bond to CPVC?

  1. #1
    DIY Member Flipperman2a2w's Avatar
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    Default Will PVC bond to CPVC?

    I have a 3/4" PVC to 3/4" CPVC adapter. I know that I have to use CPVC cement (as PVC cement is not strong enough to work on CPVC).

    Having said that, will CPVC pipe actually bond to PVC? I assume it would, since they make an adapter for that very purpose. The slip adapter itself is made of PVC.

  2. #2
    In the Trades Gary Swart's Avatar
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    Many folks do not understand about how the various plastic pipes are joined. There are 3 basic kinds of plastic pipe; ABS, PVC, and CPVC. They are chemically different. That much is easily understood. The problem comes in the fact that what we all commonly call pipe "glue" or "cement" is neither of these. They are solvents that melt the top surfaces of the pipe and fitting briefly. When the two surfaces are joined, the liquid surfaces combine into what is actually a chemical weld. So, it's not a matter of bonding, strength, or sticking. Each type of pipe has its own solvent, so the answer to your question is, No, you can't join different types of plastic pipes, except by using appropriate adapters. Not known what you are doing and why you would need to join CPVC to PVC, it's hard to advise you on what you may need to do. A couple of problems with PVC and CPVC pertain to why you are mixing media and size incompatibility. In other words, 3/4 PVC is not the same size as 3/4 CPVC.

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    DIY Senior Member Briandl's Avatar
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    I thought CPVC was typically used for supply lines and PVC for drains and vents?

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    DIY Member Flipperman2a2w's Avatar
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    Here's my situation. . .

    The water line that comes into my garage from underneath the house is PVC. I'm installing a water filtration system, and I want to add a brass hose bib to the PVC line before it goes into the filtration system (that way I can draw unfiltered water for yard maintenance).

    This is how I want to install the hose bib: 3/4" PVC main line -> 3/4" PVC to 3/4" CPVC adapter (this adapter is specifically made to transition 3/4" PVC to 3/4" CPVC) -> 3/4" CPVC pipe -> slip CPVC/threaded brass transition adapter -> brass hose bib.

    I considered using a brass hose bib with PVC, but I know you're not supposed to use a male brass thread with a female PVC thread. So, I ultimately want to use the CPVC/brass transition adapter to attach the hose bib.

    Here's what I don't understand. . . Why would they specifically make an adapter for PVC to CPVC if there's no way you can successfully join the two materials?

  5. #5
    Test, Don't Guess! cacher_chick's Avatar
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    They are not commonly found in stores, but such a transition fitting normally has a brass nipple between the 2 types of plastic. There are also plastic fittings with brass or stainless steel threaded inserts.

  6. #6
    Journeyman/Inspector Inspektor Ludwig's Avatar
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    Get a male pvc coupling and a female copper thread by cpvc adapter and screw em together to transition.

  7. #7
    DIY Junior Member Laurihill's Avatar
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    I need to find an adaptor that will tie 3/4 inch PVC to 3/4 inch CPVC. Is that a common adapter? I can't come up with a connector....

  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
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    PVC and CPVC don't mix. Inside a home, only CPVC is legal. PVC is for cold water pipes underground.

    Since they are not the same size, the only way to connect the two pipes is with threaded fittings. The post above by the inspector mentions that.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    IT would only work, and be "legal", if the two sides were different materials so their proper primers and glues could be used on each side.
    Licensed residential and commercial plumber

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