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I purchased a new bathroom sink and faucet and set everything up according to instructions. The faucet instructions told me to use silicone for the drain lip (the border thing around the stopper in the bottom of the inside of the sink, flange?).

Anyways, underneath where the pipe comes out is a rubber gasket and I've used the plastic screw on the drain pipe to seal the gasket against the underside of the sink, but when I put a little bit of water in it, some water leaks out from between the gasket and the sink. I've tried tightening it as much as I can and it still leaks.

Should I be putting silicone or plumbers putty between the gasket and the sink? If possible, I'd like to avoid taking the drain lip off because I've already sealed it there. What should I do?

Here is a picture of the underside of the sink:

enter image description here

UPDATE: It turns out (haha) that the problem was that the rubber "washer" was actually threaded itself. I'm not sure if they are always like this, but I didn't realize that it was threaded when I was assembling everything. So I assume that what was happening originally is that when I didn't have the rubber washer close enough to the basin when I started tightening the nut (blue) that it was moving the the threads out of alignment or something and not making a good seal. Once I turned the washer a few turns upwards, then tightened the blue nut, it made a proper seal. All without using a bunch of putter or silicone.

UPDATE2: So it has been 10 months and it hasn't leaked. Problem solved.

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photo?? Is it a drain with an overflow? –  UNECS Nov 13 '12 at 2:54
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Did you allow time for the silicone to cure before you put water in the sink? –  The Evil Greebo Nov 13 '12 at 3:05
    
Yes, its a drain with an overflow. I let the silicone cure for 4 hours, which is 1 hour longer than the directions. –  deltaray Nov 13 '12 at 3:26
    
Is that a metal washer between the gasket and the sink? –  The Evil Greebo Nov 13 '12 at 13:23

5 Answers 5

up vote 3 down vote accepted

It should not be necessary to try to goop some type of sealer around the lower neck of the sink drain. Such solution may work but it is not the desirable approach when you consider that someday this assembly will need to come apart for repairs.

In looking at the assembly that you have I wonder if one or more things are at play here.

1) If the drain pipe tail was not centered in the neck of the sink drain and then had lateral force on it due to the down stream goose neck trap it could be forcing the gasket open on one side. Check that there is no undue large amount of sideways pressure on the lower part of this pipe assembly.

2) It looks like the gasket directly contacts with the face of the capture nut around the drain pipe. It is possible that by tightening the capture nut that it is putting a twisting force on the gasket that may cause it to "fold away" from the sealing edge of the sink neck.

3) It is possible that there could be a small crack or pitted area on the sink neck that makes keeps the rubber gasket from engaging 100% with the sink neck.

4) Sometimes the "rubber" used in this type gasket is made of a plastic material that is anything but rubber. Check at the local hardware store to see if they have another gasket that is more pliable.

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I was wondering if maybe it was at an angle as well so I took a torpedo level too it and measured on two sides. –  deltaray Nov 13 '12 at 12:57

Sink neck poorly made allowing small leak of water dispite the gasket. I had same d... Problem today. Plumbers putty beats poor product of sink neck.

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Unless I'm very much misreading the picture you've installed your drain assembly incorrectly.

It looks to me like you've got: sink washer gasket nut

you should have: sink gasket washer nut

The gasket is soft - it shapes itself to the underside of the sink and compresses to form a tight seal. The washer is rigid and will not seal itself to the underside of the sink. You need the gasket between the washer and the sink, with the plastic nut putting pressure on the washer to evenly distribute pressure over the entire gasket.

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Or possibly the washer is missing - in which case you need it because the plastic nut isn't going to put pressure on the WHOLE gasket. –  The Evil Greebo Nov 13 '12 at 14:18
    
Gotta love a browser that zooms images. There is no washer, and the nut DOES support the entire gasket. A washer could still be useful to avoid torqueing the gasket. I think it's a matter of cleaning up the ceramic sealing surface, and possibly sourcing a more compliant gasket. –  bcworkz Nov 13 '12 at 20:19

Although it may seem like a lot of work, the best option is to take the drain apart and reassemble it. Trying to patch the leak will likely only stop it for a short time, you'll then end up with a possibly unnoticed leak sometime in the future. This unnoticed leak can lead to massive amounts of water damage, and far more work in the future. Do it right now, and never worry about it again.

Silicone is great stuff and is very useful for a lot of things, but it is not the fix-all-do-everything product people like to think it is. As you've seen, silicone is not the best option for sealing drain flanges.

  1. Disassemble the drain.
  2. Scrape all the silicone off the sink and flange.
  3. Roll out a good size bead of plumbers putty around the sink flange lip.
  4. Seat the drain flange in the putty.
  5. Tighten the drain retaining nut.
  6. Remove the excess plumbers putty that squeezes out.
  7. Repeat steps 5-6 until the drain is adequately tight.
  8. Enjoy a leak free drain.
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This is good advice but if the assembly is wrong as I think it is, no amount of putty will fix it. –  The Evil Greebo Nov 13 '12 at 13:26

Finding out why these leaks happen can be a pain, and you may not have the patience to take everything apart and inspect as to the cause of the leak. Try running a string of plumbers putty around the outside of the gasket and see if that stops the leak.

It is the quickest and easiest way to resolve a leaky gasket.

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This is a hack fix, which can lead to things like this. Take the drain apart, and do it right. –  Tester101 Nov 13 '12 at 12:18
    
@Tester101 LOL! Oh god I would never condone that :) Just a small bead around a leaky gasket and I merely suggested it as a quick fix. –  maple_shaft Nov 13 '12 at 12:29

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