I just realized the pipes below the bathroom sink are not glued or tightened in anyway.

  1. It fits into the wall outlet but I can turn it easily
  2. The light part is bigger than the dark pipe

What is the correct way to connect / tighten these 2?


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  • 1
    This is not exactly orthodox, but it is leaking?
    – bobflux
    Commented Jan 13, 2022 at 12:34
  • 5
    See diagram here for how those are supposed to work: diy.stackexchange.com/a/238932/18078 I would try to find parts to lose that accordion section, those are prone to clog and/or leak at much higher rates than smooth tube/pipe.
    – Ecnerwal
    Commented Jan 13, 2022 at 13:38
  • 1
    Can you tell us more about why you think there is anything wrong? Each of the three nuts here should have either a compression washer or a flat washer. Each of them is meant to be hand tight, which will prevent leaking but will not prevent you from moving or turning the fittings. So yes you can turn it. "Easily" is subjective. You say he dark pipe is smaller. If it's 1 1/4 to 1 1/2 that can be coupled with a special compression washer meant for exactly that. Hopefully you have one there. A compression washer is usually a translucent white plastic one that is "V" shaped.
    – jay613
    Commented Jan 13, 2022 at 18:09
  • There is water accumulation in the cabinet from time to time. At first I didn't know where it comes from because I run my hand along the pipe but didn't find it. But now I'm 90% sure it's from #2 because there is gap between the dark pipe and the light one. I guess my question boils down to "how to connect pipe of different size". What plumbing part should I get
    – Motoko
    Commented Jan 14, 2022 at 0:28

2 Answers 2


You should be able to turn both of them clockwise to tighten. They both should have a tapered hard rubber/plastic or black rubber gasket that is squeezed and tightens around the inner pipe (the male part of the fitting) to create a water tight seal.

Comment About Tightening

What I do it to tighten them up as much as I can with my hands. It's almost impossible to overtighten with hands given the awkward position of the nuts. Then I run some water and check for leaks. If any leaks show up, then I come back with a wrench or big pair of pliers and tighten the offending joint a bit, maybe 1/16 of a turn and recheck. Have to be careful because too much force can distort and damage the gasket.

Also, you should get rid of that flex coupling. You should be able to find some combination of rigid pipes and couplings to use there.

  • 5
    Very important to NOT over tighten the slip rings - that will cause as much leaking if not more than a loose one, and it will require replacing parts. Also, a vote for getting rid of the flex pipe. They're a mess.
    – FreeMan
    Commented Jan 13, 2022 at 14:10
  • +1 for pointing out that if you try to immobilize the joints by over tightening they will probably leak!
    – jay613
    Commented Jan 13, 2022 at 18:12

As an alternative to SteveSh's answer, the simple solution to the drain tailpipe problem is you probably have 1 1/4" there and the rest of the drain assembly is probably 1 1/2". You could just install a reducing washer at the part that pulls off and call it good (this would be the cheapest solution). No, the flex pipe isn't good, but none of it seems to leaking or problematic (for now).

If you're looking for a better fix, pull the tailpipe from the wall, reduce it to 1 1/4" there, and then re-plumb everything to the sink pipe. Shouldn't be expensive, but you will have to get creative on the drain fittings since they don't line up.

  • Thank you. I will go get some reducing washers!
    – Motoko
    Commented Jan 14, 2022 at 1:13

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