Gluing DWV test caps

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by bmwpowere36m3, Jul 27, 2014.

  1. bmwpowere36m3

    bmwpowere36m3 Member

    Messages:
    43
    Location:
    CT
    I assume these just get glued into the stub-outs. Should I first use primer on these, like a typical PVC connection?

    Once the water test is completed, they are knocked out... I assume a little ring, from the test cap, remains in the pipe's ID. No issue there right?
  2. asktom

    asktom Member

    Messages:
    575
    Location:
    Victor, MT
    I'd use primer. As for the rest, you've got it right.
  3. Tom Sawyer

    Tom Sawyer In the Trades

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    Maine
    Never use the damn things. They always either leak or blow out. Use the rubber French type or the internal plug with the wing nut.
    johnjh2o1 likes this.
  4. Terry

    Terry Administrator Staff Member

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    15,125
    Location:
    Bothell, Washington
    In the Seattle area, we mainly us ABS.
    I haven't tried test caps on PVC.

    With ABS, you can hold three stories of head pressure easily enough. For a lav or kitchen stub out, we cut the ends off anyway and glue the trap adapter at finish.
    If it's a closet flange for a toilet, well...........your horn of a bowl is way less than that seam anyway.
  5. Tom Sawyer

    Tom Sawyer In the Trades

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    Location:
    Maine
    Terry, I think he's talking about the ones that have a flange and glue to the inside of the pipe. I've never seen them for ABS but maybe someone has them.
  6. hj

    hj Moderator & Master Plumber Staff Member

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    The ones we use on ABS are white, but are glued with ABS cement.
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,125
    Location:
    Bothell, Washington
    That's what I use. We call them test cookies. Don't bother looking that one up. It may be a local thing.
  8. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    I've used them a couple times (yellow for PVC). I used primer and cement. They worked okay for me. I also used the wingnut type as well as the test balloons (depending on location). I don't have the experience that these other guys have...just giving you another DIY viewpoint.

    They worked fine for me, but I like the wingnut type better. The knockout ones are much cheaper, but you also have to be careful when you knock them out to avoid pieces falling into the drain.

    The funny thing is after I did all my pressure tests, I was in HD looking for some other pieces. I overheard another customer talking to the "plumbing guy" that worked the aisle. Sounded like he installed a washer + utility sink. The utility sink wasn't hooked up and he wanted to cap it, so he could use the washer. They were both looking up and down the aisle for something to cap it. I mentioned that he could use the wingnut plug (and explained how they work and what they are for). The "plumbing guy" said "Oh...that's what those things are for! I always wondered what those were.".
  9. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,227
    Location:
    Maine
    I've just never had good luck with them. Seems like if theirs a test leak, that's where I find it. Besides, the rubber ones I can reuse over and over.
  10. bmwpowere36m3

    bmwpowere36m3 Member

    Messages:
    43
    Location:
    CT
    I should elaborate... I'm redoing my entire home (single story ranch) in schedule 40 PVC for DWV. While not required by the inspectors, I want to perform a leak test before putting up sheetrock. For the most part I can either use rubber expansion plugs or plastic test caps (flanged white PVC cap). Obviously the test caps are much cheaper, on the order of 20 cents vs. $2-4 for the rubber plugs.

    [​IMG]

    So I'll primer and glue them in place. I just assumed when properly glued, after they are knocked out a little ring/flange will remain in the pipe's ID. The toilet flange already has a knockout built-in.

    I have one tricky spot to try and block off and I'm not sure how to do it. It is a 3" combo where the vertical main stack ties in and horizontally thru a fernco coupler ties to the cast iron pipe in the foundation. Since its all assembled/glued/secured I cannot pull the combo away from the fernco coupler.

    What can I use inside the combo (has a cleanout on the end) to block it off? Otherwise the water will just run out into the sewer line.

    plumb1.png
  11. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,227
    Location:
    Maine
    Yep, those are the ones....good luck.
  12. asktom

    asktom Member

    Messages:
    575
    Location:
    Victor, MT
    You do need a smooth straight cut (I use a tube cutter and never had a problem). Usually the only one knocked out is the toilet, the rest are normally left a little long (too long is better than too short) and cut off.
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