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Thread: one more ??? schedule 40 pvc

  1. #1
    DIY Senior Member coach606's Avatar
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    Default one more ??? schedule 40 pvc

    1) What's the difference between schedule 40 pvc and, well, regular pvc that I might find at Lowes? I was looking online at a plumbing supply store for a
    4 x 4 x 3" wye to use on my basement stack with no hub couplings. I noticed that the online store only sold schedule 40, 4" x 4" x 3" Wyes for like $40 - $50. I found the same item, probably not schedule 40 at Lowes for $8.

    Do you need schedule 40 pvc for use in a 4" stack transitioning to cast iron?

    2) I was planning to cut out more room than I need to put my wye into the stack and to use 4" pvc with no hub, shielded couplings to the cast iron, then cement the hubbed 4" x 4" x 3" wye to the straight pvc pipe.

    Is this a good plan?

  2. #2
    In the Trades Bob NH's Avatar
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    Default

    The 4" pipe in the store is almost certainly Schedule 40 PVC. That is used for Drain/Waste/Vent as well as pressure pipe.

    Plumbing fittings are marked DWV (Drain/Waste/Vent) to indicate that they are not pressure fittings.

    The on-line place may be selling Schedule 40 pressure fittings. They are not acceptable for DWV because they don't have the smooth internal flow passages required for DWV. They are more expensive because they contain more material and they are rare.

  3. #3

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    "What's the difference between schedule 40 pvc and, well, regular pvc that I might find at Lowes?"

    The Big Box stores sell Sch40 PVC andl thinner-walled pvc pipe that is really only appropriate for downspout routing. Some of the thin stuff also has flared ends so you can couple many together without fittings.

    Are you sure the fittings you saw on line weren't for a pack of 6?
    Last edited by prashster; 07-07-2006 at 06:14 AM.
    (important note: I'm not a pro)

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default fittings

    DWV fittings, which are all that you should use for a drainage system are "necked down" between the hubs so the internal passage is the same size as the interior of the pipe to create a smooth flow. Pressure fittings are heavier to handle higher pressures, but create a disruption if used for drainage. They also do not have the "sweep" that is required for drainage connections.

  5. #5
    DIY Senior Member coach606's Avatar
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    Default Thanks...

    I was looking on **************.com and the 4 x 4 x 3" wyes they had were like $40. In their FAQs they explained why their wyes were so expensive. The answer was that most other wyes were not schedule 40.

    I guess they are. You guys are great. Thanks for answering my question. I'll be sure to use the correct pipe.

    The selection at Lowes is actually pretty good.

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