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Fitting HDPE conduit to ABS

KYLE WINSTON BENTLEY | Posted in General Questions on

I recently came across a bit of HDPE conduit that I’m hoping to reuse, but I’ve never worked with it before.  It’s schedule 40, smooth wall Duralime. If I wanted to use this in an underground run, and joint back to ABS on both ends, are there special fittings required in the NEC?  Solvents? Primers?

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Replies

  1. Expert Member
    BILL WICHERS | | #1

    You can’t solvent weld to HDPE. The normal way to put connectors on is to get compression fittings for the conduit you’re using. Splices are normally made by fusion, which is done by using a special machine that melts the two pieces together with heat. You can get the connectors from utility supply houses. I’d probably call Graybar and ask them, they are national distributor and should have a branch in your area. Note that they have an electrical division and a telecom/utility division, which typically have separate buildings. You want the telecom/utility division for this type of material.

    What you’ll probably need to do is put threaded connectors on the HDPE pipe, then used threaded connectors on the ABS pipe so that you can mate the threaded connectors together to make your final connection.

    Bill

    1. Expert Member
      KYLE WINSTON BENTLEY | | #2

      Bill,

      Is this type of item what you're describing? I thought conduit was expensive, but sheesh.

      https://hdpesupply.com/2-ips-hdpe-compression-x-2-pvc-compression-transition-coupling/

      I also see these, but am unsure if fitting on a PVC is 'kosher'. Just FYI, this is to house cable that is already rated for direct burial, as a bit of future proofing.

      https://hdpesupply.com/2-ips-compression-x-2-male-threaded-transition-mpt/

      1. Expert Member
        NICK KEENAN | | #4

        To be used in electrical a fitting has to be UL listed for that purpose. There is a bit of a gray area when materials are used for wire protection, they don't have to be listed. The extreme example is a buried line, if it's buried deep enough dirt is sufficient to protect the cable but dirt isn't a UL-listed material.

        If you're using conduit as conduit -- to allow you to avoid having to bury the wire so deep -- then I'd say the fitting have to be UL. But if the installation is compliant without the conduit then the conduit is just a piece of pipe you're using to guide the wire and can be anything. Just my opinion though. Your inspector gets the final say.

      2. Expert Member
        BILL WICHERS | | #5

        To address what DC said, that's not entirely correct. Conduit doesn't necassarily mean you can bury things at reduced depth, and burying things deeper doesn't necassarily mean you don't need conduit. An example is that direct buried cable must be listed for use directly buried. You cannot directly bury cable that isn't listed to be installed that way. Conduit has to be buried at code depth too, with the exception of rigid steel (which isn't EMT, it's RMC, "rigid" here doesn't just mean "stiff").

        For the underground duct, if you want to run power in it, it has to be UL listed. If you want to run telecom cabling (Ethernet, fiber optic cable, etc.), then it doesn't have to be UL listed. If you want to run power in it, you're supposed to use UL listed fittings too. What I have done in the past is to use PVC fittings and silicone the HDPE pipe into the fitting. This won't hold for pressure, and ins't technically "correct", since the fitting isn't really listed for use with HDPE pipe, but it works and I've never seen anyone look closely enough to fail it. The fitting says "UL", and if the pipe does too, that's when the inspector stops looking. The downside is the silicone doesn't really hold very well, so extreme frost heave could disconnect the fitting. You could potentially pin the pipe and fitting together with a small screw, but that would void the UL listing so it's not really an option if you're running power cable.

        If you want to run potable water, you have to use the right fittings since they have to hold pressure. Typical adhesives won't bond to polyethylene, which is what the "PE" part of "HDPE" stands for, so my silicone trick won't hold pressure for a water line. For electrical stuff, you just need to keep things from coming apart easily so the fastening of the connector is much less critical.

        BTW, that conduit you have says "COMCAST" on it, so it's probably some scrap from a Comcast install. You should have no problem using that for your own telecom cables, but if it doesn't have the UL mark on it, it's not really correct to use for power. When I spect underground HDPE duct for power, I spec schedule 40 or 80 UL listed conduit, which is listed for use with power cables. Those ducts are usually either black or black with red tracers, but you can get many color options. Orange is common for telecom. DO NOT USE YELLOW HDPE PIPE. Yellow is reserved for gas lines (and petroleum) only.

        Bill

        1. Expert Member
          KYLE WINSTON BENTLEY | | #7

          Bill, DC,

          Thanks for the tip on the UL listing. I pulled the tech data sheet down from their website, and it is in fact UL listed, along with a few other specs I don't immediately recognize -

          "SPECIFICATIONS All Smoothwall conduit dimensions meets or exceeds one or more of the following:
          ASTM F-2160, ASTM D-3350, ASTM D-2239, ASTM D-3485, NEMA TC-7, UL 651A, UL 1990, Bellcore GR-356."

          It's branded comcast, in fact they donated it to me, when their contractors dumped a load of this stuff in an undeveloped part of our HOA >:(.

          Reduce, Reuse, Recycle..

          Just to clarify, I'm wanting to use this for a housing AL 2224 direct burial wire, at the same depth I would have otherwise burried it, no pressure or any type of fluid system.

          Thanks!

        2. Expert Member
          NICK KEENAN | | #8

          Bill, let me explain further what I mean. Direct burial cable requires (generally) 24" of cover, non-metallic conduit requires 18". So if you only want to dig down 18", the non-metallic conduit you use has to be UL listed for burial -- including the fittings. However, if you're down 24" and using direct burial you can put whatever you want on the cable to make laying it easier. For example, if you're down 24" and want to go under a walkway without digging it up, you don't need to use a UL conduit, you can use whatever's handy so long as it doesn't damage the cable. And there's nothing in the code that prevents you from adding more protection than the code requires, so long as you're not trying to do it instead of what the code prescribes but rather in addition.

          Similarly, there are a lot of places where the code talks about "locations subject to damage" -- which is a very vague phrase. You don't have to use UL materials to change a "location subject to damage" to one that's not subject to damage.

          So tying back to the original question, it's an important detail whether the OP is trying to use the conduit as UL-listed non-metallic conduit, or just as a way of simplifying the installation and adding additional protection.

          1. Expert Member
            KYLE WINSTON BENTLEY | | #9

            We must have posted at the same time, see my reply to bill.

  2. AlexD2022 | | #3

    I've been looking into this too, for tying some drainage HDPE pipe into pvc elbows. It looks like it is possible to pick up glue (NOT solvent weld) that will stick to HDPE and PVC, however I'm not sure how strong the glue will hold.

    1. Expert Member
      BILL WICHERS | | #6

      It won't hold well. If you are putting together a gravity drain, you'll probably be OK. If you're going to run even moderate pressure (like a sump pump into a 100 foot pipe or something like that), you'll probably have problems with leaks at the fitting. I would recommend using a proper compression fitting in this case.

      Bill

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