Clean pipes vs. leaky sink

August 23, 2009 10:41 AM

What did I botch when reconnecting the pipes under my kitchen sink, causing them to start leaking? Picture included below, with the leak indicated.

So, I pulled out the trusty auger to unclog a slow draining sink, and retrieved a bunch of gunk from the pipes. TMI? Anyway, I cleaned out a bunch of crud that had accumulated along the pipes as well, and reattached the pieces. In this picture, you can see the culprit - it's a p-trap that should just screw on to the next bit. Unfortunately now, there's a small leak right in the inside U. Have I not tightened it enough, or is it too tight? Is it not aligned properly? Is there a washer missing in there (don't think this is the case, but IANAP)?

Please help! My wife is angry that I'm doing dishes in the laundry sink downstairs! :(

posted by swrittenb to home & garden (14 comments total)

Go to the plumbing store and buy some teflon tape. It's thin and has no adhesive. You wrap it all over the threads of the male side before screwing them together, and it seals the joint.
posted by Chocolate Pickle at 10:46 AM on August 23

Is that a permanent sealant? Should I worry about getting back in to the pipes in the future?
posted by swrittenb at 10:48 AM on August 23

If I had to guess, you broke the seal on to the horizontal pipe on the right of the above image. It's probably an hour to fix and a run to home depot to buy a new set of pipes aqnd you'll be out 10 bucks. You can also try and unscrewing the joint and check the plastic washer that should be there with it or just replace that. The other option is teflon plumbers tape what can help make a better seal, but it's generally compression that holds this all together in my experience.

finally it is also possible (contrary to the advice above) that you have overtightened aqnd have too much compression that is preventing a clean seal. You really need to figure out if the leak is coming from that joint or another one...I suggest putting some paper towels around the joints or pipes and putting some red food coloring down the drain to see if it helps you identify where the leak is coming from.
posted by iamabot at 10:52 AM on August 23

Teflon plumbers tape is non permanent, it's generally used for mating fixtures to their feed pipes, the most common place you will generally see it is around the pipe that a shower head attaches to, or under your sink connecting the feeder lines to the faucet hot and cold lines. All it does it insure there is a good seal, doesn't make it permanent.
posted by iamabot at 10:54 AM on August 23

Telfon tape isn't permenant, and, if anything, it actually makes things easier to unscrew in the future.

If I were you I'd take stuff apart again. Check for any damaged seals/washers/rings and flanges. I suspect that there is a flange at that joint that isn't seated right. one of the pieces might be at too much of an angle When reassembling it, I'd start hooking everything up loosely, then going back through and tightening things up, trying to ensure things are positioned squarely.
posted by Good Brain at 10:54 AM on August 23

These are really great tips - thanks! I'm going to head out in about an hour or so to pick up some teflon tape. I've screwed and unscrewed a few times, and the leak seems persistent (although I can vary the amount to some non-zero value). A lot of the other connections have been sealed with some permanent sealant, so if it became a problem with a crack in some of the sealed piping, would I have to actually break out the Dremel to get those pieces off? Why are most of the seals cemented, and only one subset removable? Is it to keep jerks like me from screwing things up like this?

Thanks again everyone, I'll post back with the results.
posted by swrittenb at 11:02 AM on August 23

There should be a beveled plastic o-ring under the nut that encircles the smaller diameter drainpipe. As you tighten the nut (gently), this ring compresses around the smaller pipe and seals the joint.

Most of the seals are cemented because you do not need to take them apart to snake or auger them. The P trap disconnects because it is most likely to trap junk and most likely to clog.
posted by kuujjuarapik at 11:17 AM on August 23

A little googling tells me the part is called a slip joint washer.
posted by kuujjuarapik at 11:21 AM on August 23

Problem solved, thank you AskMeFi!

I'd tried to fit one of the slip joint washers (thanks for the name, as well!), but it didn't really seem to fit properly. Either it was too tight, or I was just flat out doing it wrong. Some teflon tape wrapped around the male end of the piping combined with a firm gentle screwing fixed it right up. Gosh, that sounds dirty. And hey, it was dirty; on recollection, some gunk that came out originally could easily have been tape that had previously been used on this particular spot. The leak is gone.. but for how long..

Thanks again! I'm just glad we didn't have to resort to some more serious pipework.
posted by swrittenb at 11:54 AM on August 23

For future reference, this really isn't an appropriate place for teflon tape. It may work for a while, but the seal is supposed to occur where the outside-beveled end of one pipe is pulled against the inside-bevel of the other pipe. The threads of this joint are used only to pull the parts together; the threads themselves shouldn't need to be waterproof because water should never get past the mating bevels. Since it's not working as designed, one of the parts might be damaged (cracked, chipped, scratched somewhere on the bevel) or other parts of the plumbing may be slightly out of position, making it impossible for these parts to align properly.
posted by jon1270 at 3:32 PM on August 23

Everyone keeps saying that teflon tape isn't permanent, but I've never had a joint leak after I used it, even after many years.
posted by Chocolate Pickle at 4:28 PM on August 23

By "not permanent" I think they mean it will not glue the threads together, thus preventing disassembly. It will continue to remain sealed indefinitely unless the joint gets mechanically wiggled about or unscrewed.
posted by polyglot at 5:15 PM on August 23

Ah, I see. Yes, that's correct. Teflon tape will not make it difficult or impossible to unscrew again in future. On the contrary, as mentioned above it's actually a bit easier.

But it won't degrade and start leaking if the joint is left alone. Teflon doesn't rot or degrade. That's why it's used for this.

If, sometime in future, you do have to take that joint apart again, you'll need to clean the old teflon off the threads -- usually you can just wipe the threads off -- and apply more tape before screwing the joint together again.

But if you leave the joint alone, it should be fine for years.
posted by Chocolate Pickle at 6:08 PM on August 23

I just completed a plumbing repair job. I had to disassemble it, and reassemble more carefully, twice due to leaks. It seems to be the rule, for me, that the number of leaks decrease with each subsequent fix.

Teflon tape is your friend. Be sure to wind it the proper way on the threads. Otherwise, it gets bunched up and does you no good.

With the p-traps, I find that new gaskets are best for each time you take them apart.
posted by Midnight Skulker at 8:29 AM on August 24