Heard what sounded like water slowly dripping from stairwell outside the 2nd-floor bathroom when the bathtub is draining. Following sound location down to the 1st floor, discovered a black drainage pipe with soaked floor and stud but no water on the outside of the pipe. When I opened up the wall on the other side I found that the pipe was wet. Later when the shower was used in the 2nd upstairs bathroom, I checked the pipe and found it was wet on one side. I am thinking there is likely a leak at the joint where the line changes from vertical to horizontal since there is leaking whenever draining water from both bathrooms. Am I on the right track? If I am correct and find the joint leaking is reapplying the joint glue all I need to do or will I need a plumber?

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    I think you need to pour buckets of water directly into the drain and see if that leaks, or if you have a hand-held shower, spray it only on the drain. It's possible there is a leak on the wall tiles or corners of the shower that might look like a drain problem.
    – JPhi1618
    Commented Feb 10, 2020 at 16:03
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    Black is generally abs pipe. It is fairly rare for it to develop a leak - the more likely culprit will be caulking or a supply cartridge in a shower. Commented Feb 10, 2020 at 16:37
  • I have two bathrooms upstairs and there is water coming down the pipe no matter what drain is being used; both toilets, both sinks, the bathtub in one bathroom and the shower in the other bathroom. Which is why I am thinking it is a leak at the joint of the pipe. I have had a leak problem with the bathtub shower and the leak came from right under the bathtub. I will be removing the the ceiling this weekend to try and find out what is leaking. Thanks for letting me know it is called abs.
    – KC57
    Commented Feb 13, 2020 at 20:19

2 Answers 2


Usually if it is a joint leak with PVC or ABS piping it is the best to cut out the failed parts and replace with new properly glued parts. The PVC or ABS parts are relatively inexpensive and can actually be a reasonable DIY project to replace.

The type of cement used to join PVC and ABS pipes to fittings is a solvent that softens the surfaces and then when they are slid together they weld as one. It is not at all effective to try to smear more of the solvent onto the outside of a joint. In addition to that PVC ans ABS materials have the characteristic that many other types of glues do not effectively adhere to it.

You may be able to do a temporary type of repair if you clean and dry the area very well and then apply some silicone sealer to the leak area. Silicone sealer will adhere to clean dry PVC/ABS but if it is wet then it will not. This is only temporary and a proper fix as outlined above should be done as soon as reasonably possible.


Simply applying solvent (i.e. "joint glue") to the outside of the joint will not result in a permanent fix. If the joint was improperly done the only fix is to disassemble the section and fix it. Generally this means cutting the bad parts out since you usually cannot pull badly assembled joints apart, and then putting new and correctly joined parts back.

If you're not comfortable with these procedures, you may be better off calling a plumber.

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