Gluing DWV test caps

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BMWpowere36m3

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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?
 

Tom Sawyer

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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.
 

Terry

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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.
 

Tom Sawyer

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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.
 

Terry

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That's what I use. We call them test cookies. Don't bother looking that one up. It may be a local thing.

cherne_clean_seal_plug.jpg


I also use these on test tees. You can thread them in, pump them up, and they will hold a test.
 
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Nukeman

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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.".
 

Tom Sawyer

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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.
 

BMWpowere36m3

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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.

611942052851lg.jpg


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
 

Asktom

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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.
 

chris6719

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I know this an old thread.

I need to do a pressure test for my DWV. If you cement the plastic plug into a pipe, after knocking out the center, wouldn't the ~1/8 ring left inside contribute to a future clog? I would rather not have to glue and then cut off the stub after the test.

Thanks in advance,
Chris
 

Terry

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I need to do a pressure test for my DWV. If you cement the plastic plug into a pipe, after knocking out the center, wouldn't the ~1/8 ring left inside contribute to a future clog? I would rather not have to glue and then cut off the stub after the test.
Chris

For lavs and sinks, I'm cutting off the stubouts anyway.
Places I may leave the test cap are at the closet flanges and the showers. There hasn't been a problem either way with the little rim left in there after knocking out the caps.
 

Kreemoweet

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I would rather not have to glue and then cut off the stub after the test.

Then don't use glue-in plugs. Mechanical expansion plugs, pneumatic plugs, rubber caps, and threaded caps all work quite well (and better than those
glue-ins, in my experience).
 

hj

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There is NO "1/8 ridge" inside the pipe when you knock the cover off. It is about 1/64", the thickness of the plastic. For the main line, you use an inflatable test ball with a hose on it.

cherne_long_test_ball.jpg
 
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LesP

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I did a trial water pressure test of my new ABS lines using those white knock-out caps at each of the stub outs. Happily the ABS joints all seem to be holding nicely, but two of the test tee caps were spritzing water where I apparently did not achieve a full seal at the cut edge of the pipe.

My question is whether there is a way to seal the gaps in the caps without having to cut them off and add new ones. My stub outs are not that long and I'm concerned that cutting the pipes in place will result in a less even cut than the first time. Could I put ABS glue or JB Weld around the outside edge of the caps to close off the tiny gaps in order to pass the pressure test?

Thanks, as always, for your guidance!
Les
 

Reach4

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I did a trial water pressure test of my new ABS lines using those white knock-out caps at each of the stub outs. Happily the ABS joints all seem to be holding nicely, but two of the test tee caps were spritzing water where I apparently did not achieve a full seal at the cut edge of the pipe.

My question is whether there is a way to seal the gaps in the caps without having to cut them off and add new ones.

i159100-3.jpg
Test tees like this?
 

LesP

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Nope, like the picture in reply #9 above...the translucent white knockout caps. They have a thin little gluing surface &/or I didn't use enough glue.

There is an ABS tee like in your picture at the end of the line but that is being blocked nicely by a 3" Cherne Clean Seal.
 
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