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I have an ABS pipe fitting under my kitchen sink which appears to be held on by friction (white piece just above the p-trap). After the p-trap the pipe makes a long run to the left where it's not really supported by anything. It seems the weight of this run caused the pipe to slide down off the drain pipe, causing a huge gusher.

I'm not totally sure how this is intended to work, but it seems like the white fitting just holds the p-trap and everything on by friction? If so, what should I do - replace the white piece? Anything else? Also, how do I know what the correct height of the fitting and slope of the lateral pipe should be. The lateral pipe was fairly level before, but a friend noted that ideally it should slope a bit. Not sure if I'll mess anything up by adding slope.

(Note: zip-ties in the pic are my temporary safeguard).

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Unscrew the white compression nut and take a look at the sealing ring that is under it. These can get hard with age or over compressed and lose shape and thus lose its ability to squeeze tightly to the down drop pipe from the sink drain. If this is the case it is an indication that the sealing ring needs to be replaced.

The common type of the sealing ring is made of a nylon material whilst the orange colored one (purchased at big box store) is made of a more rubbery type plastic that will compress and squeeze much better under the compression nut. (In the picture I have cut the nylon part to show it's wedge shaped cross section). I have also seen the rubbery type wedge rings in a blue color as well. These better rubbery sealing rings cost more than the nylon types but are far superior in my opinion.

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When you take apart the slip joint do take care to clean out the joint and the outside of the drop pipe to remove any old drain gunk and soap scum. A nice clean setup will result in the best seal of the wedge shaped sealing ring against the drop pipe.

  • Note that it is common for drain type P-trap kits to come with the cheaper nylon type wedge rings. I always throw these away and buy packages of the rubbery type to replace them. It results in less leaks and far more secure drain connections under my sinks. – Michael Karas Apr 21 '15 at 9:07
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The white fitting should be on top of a small compression ring, so when reassembling the pipes you would add the white female threaded fitting, the compression ring (thin side pointed down), and then the black male threaded side of the fitting. When you tighten this by hand, the compression ring will get squeezed between the two pipes and make a water tight seal.

For the slope, 1/4" per foot of run should be your target.

  • What does it mean that the entire setup fell off - that the compression ring needs replacing? Or the white female fitting? – Jonathan Apr 21 '15 at 2:30
  • May have been too loose. Despite the fact that you're supposed to only hand tighten them, I gently give them an extra 1/4 turn with some channel lock pliers after I get it snug. Could also be too much movement on the pipes there, you don't want items hitting the plumbing that you are pulling in and out of that cabinet. – BMitch Apr 21 '15 at 3:29
  • No way of knowing how tight it was before so... should I replace or just tighten? – Jonathan Apr 21 '15 at 3:52
  • Like Michael says in his answer, replacing the inner ring is a good idea, they're cheap and easily lost when the joint comes apart. – BMitch Apr 21 '15 at 14:59

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