I installed a new faucet and tail pipe in a bathroom sink. It leaks where the tail pipe collar connects under the sink. I have done this type of bathroom faucet replacement probably 6 or 7 times over the years, so I know you can under tighten and over tighten the collar under the sink - the rubber gasket can get out of wack if you tighten the collar too much. But even knowimg that I can not get it to stop leaking right there. I have dismantled all of it a couple times, reapplied a rope of plumbers putty each time up top, made sure the new rubber gasket is inserted properly, tightened it down, and it still leaks.

I have no other ideas and it is getting frustrating. Yes I could call a professional out but I feel like I am so close. Plus I have to do the other sink’s faucet next (it’s a double sink countertop). Any ideas?

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  • Even though the gasket is brand new, have you tried a replacement? It could have been damaged, right from the factory.
    – FreeMan
    Commented Nov 9, 2020 at 11:29
  • Yeah, I'd be looking for a nice fat, juicy neoprene washer with lots of coverage.
    – isherwood
    Commented Nov 9, 2020 at 17:27
  • Any idea where I can find, as isherwood suggested, a nice fat juicy neoprene washer with lots of coverage? I tried a local plumbing wholesale supply company, Home Depot, and searched online quite a bit with no luck. I need one that is 1 1/4 inch ID and 2 1/2 inch OD or more.
    – Mark Z
    Commented Nov 11, 2020 at 4:39

2 Answers 2


From the photo it looks like the tailpipe is misaligned with the hole in the sink (collar offset to the right so that it overhangs the sealing surface of the sink on the right and barely covers it on the left). This is quite a common issue and if the offset is bad enough, the gasket won't even have anything to seal against on the left side and instead the collar will just force that part of the gasket into the hole.

This issue can also be made much worse if the gasket is a bit too small for the collar and the hole. I'm used to the outer diameter of the gasket being at least about the same as the outer diameter of the collar.

Try realigning it to see if you can improve the situation. If the only way to get the collar and the hole aligned is to tilt the tailpipe, it's likely you'll get another leak due to the two sealing surfaces not being parallel (so that when the collar is tightened just enough for one side, the other side still has a big gaping hole). If that happens, just use a thick-ish gasket of the "spongy rubber" variety, which tends to compensate for these issues much better than solid rubber gaskets.

A good way to look for leaks is to tighten the collar just lightly (so that it doesn't fall off and the gasket is held in place), get a strong light source (a powerful flashlight or something) and shine it down the sink. If you see any light shining through anywhere near the gasket, that's where a leak will likely occur once you tighten properly.

  • 4
    When aligning the tailpipe to the sink, make sure the bottom pipes are not connected. You should be able to align the tailpipe centered to the sink hole and then tighten the connection. After that, then connect up the rest of the pipes. Commented Nov 9, 2020 at 15:30

I had the same problem when putting in a new sink drain. The problem was the hole in the sink had a rough irregular surface . I fixed it by sanding the sink smooth so the pipe dope/caulk around the sink drain could seal better. I guess the original drain must have used a lot of dope.

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