DWV testing and mysterious leak- solved

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Cacher_Chick

Test, Don't Guess!
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Thought I would share this as it might prevent others from suffering through the same hassle.

I'm pre-testing my new bathroom DWV in preparation for inspection. The inspector requested to see a 5 psi air test of the system. This is normal under Wisconsin code.

I have spent WAY too much time trying to get the toilet riser to seal. I first tried an Oatey test plug, then a Souix Chief, both of which I could not get to seal. So, I installed a $.75 glue on test cap, thinking that would be the end of it. No dice.

I took a break and thought about things for a day before I was feeling enlightened once again. Returning to the task at hand, I learned something today.

Cellular core PVC will pass air THROUGH THE CORE. The air is passing through the foam core of the PVC. I'm sure some of the regular plumbers have seen this, but it was enlightening to me. I thought nothing of buying the cellular core PVC, as it is the only thing stocked in the stores around here.

No matter how much we might think we know, sometimes, we have to learn the hard way.
 

Kreemoweet

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Just dropped by to corroborate cacher-chick's observation. Couldn't figure out why an air test would never hold pressure, but water always worked, with
no leaks. Covered the test plug in a shower drain with some water, and saw lotsa tiny air bubbles coming through the cut end of the (foam-core) ABS pipe.
Mysterious!
 
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Hey, wait a minute.

This is awkward, but...

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