The drain in the sink which we use for mouthwash consistently gets clogged by a very repugnant slime. I've tried all the common drain unclogging products (Drano, Liquid Plumber) as well as some non-standard remedies (e.g., boiling water, vinegar + baking soda), but none of them seem to help. Which means that once a year I have to disassemble the entire drain/trap assembly and manually scrub out the pipes. Can anyone offer another remedy?

(Note: as I've mentioned, this only happens to the sink where we use our morning mouth wash. We tried using a different sink -- to confirm the theory -- and sure enough, the bio-slime began to build-up in that sink instead. It is apparently caused by the bacterial discharge that is expectorated with the mouthwash.)

UPDATE: I've discovered that the slime only seems to grow in the presence of water. So my initial habit of running the faucet after spitting was actually counter-productive. I now resist the urge to rinse out the mouthwash and it seems to have solved the problem.

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    You mention 'drain unclogging products', but have you tried any of the 'slow drain' products? Most require you to leave them for hours to work, but they're designed for this sort of stuff. Most mention enzymes on the packaging.
    – Joe
    Commented Aug 29, 2011 at 3:25
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    Is it feasible to spit into something else? If this is a bathroom sink, could you spit into the toilet instead? It sounds like the sink in question just isn't getting much traffic, so things aren't getting rinsed away. So if spitting ino the toilet is too gross, could you move some other regular action (shaving, rinsing things) to the troubled sink? Commented Sep 1, 2011 at 12:59
  • I have noticed this in all my sinks, which I clean about every 6 months or when they start clogging. I recently noticed a black mold growing on the cutlery tray in my dishwasher. The machine is about a year old and all stainless inside. When I examined closer, the black slime was in all the spray heads and drainage of the machine. This rules out mouthwash. I have read that the slime can be dangerous to your health so I would suggest calling a plumber for help.
    – user18332
    Commented Nov 27, 2013 at 19:37

9 Answers 9


This has been an ongoing problem in the bathroom sink we use the most. When I was using conventional solutions (Drano and the like) to unclog it, I just assumed that there was a bunch of hair in the drain. This was a problem every couple of weeks, though, and I hated spending so much money on toxic drain cleaners. A couple of years ago, I happened across a long and flexible, toothed tool called Zip-It at the hardware store, and I've not had to invest in drain cleaner since. Since this tool pulls whatever's clogging the drain out of it, I learned that it wasn't only hair causing the sink to backup - it was also tons and tons of black slime. It's pretty gnarly, but it's satisfying to know that I'm actually physically removing this stuff from the drain! I saw that the tool is sold online as well, and I noticed that it's marketed in some places as a one-time use tool, but that's ridiculous. I've used the same one since I bought it two years ago, and it still works as it should. It's really cheap, though (I think I paid $3 for it), so even if the teeth do break off, it's easy enough to buy another one.

That drain still clogs with black slime every couple of months, and even though I can pull it out, I'd like to prevent it if possible. So, I'm going to start using baking soda + vinegar + hot water to see if that works to prevent it.

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    Zip-Its are great! Disgusting to use, but great. I've been using the same one for 5 years. I've gotten pretty good use out of the $3 tool.
    – Doresoom
    Commented Aug 11, 2015 at 19:20

I attached 12" plus or minus of electrical copper wire to my drain plug. Copper kills the bacteria. I have not had a problem since, and it has been 4 years.

  • This is fascinating. I read recently about a company trying to sell elevator buttons as they would help reduce the transfer of germs. I may try this in my shower. I have the slime problem there.
    – Evil Elf
    Commented Aug 10, 2015 at 12:08

Ordinary Drano and other clog removers are formulated mainly to dissolve hair and soap scum. For "bio-slime", you need something a little different. Look for "buildup remover" or "foaming pipe snake" products in the same area of the store as basic liquid drain openers. Use as directed, and they'll help considerably.

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    I've had good results with liquid "foaming pipe snake", followed by a lot of hot water (filling the sink partway) followed by vigorous use of a plunger. The plunger will bring up a lot black gunk which was loosened by the foaming pipe snake, which you can then wipe up. Commented Sep 8, 2011 at 1:47

If it's a slime (i.e. something alive) you might want to try pouring some bleach down the drain to see if that helps. A couple of gallons of bleach shouldn't bother a municipal sewage line, but it might affect a septic system.

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    The slime is likely only in the p-trap, which may require a cup, at most, of bleach.
    – DA01
    Commented Aug 3, 2012 at 22:11

Bioclean applied monthly would do the trick, and is meant for sewer pipes.


I know that this is a very old post but I came across it recently when I started having the problem. Not sure what exactly causes it seeing as I didn't have issues before in previous houses. Only thing I can think of is that the sink in this house gets a little more foot traffic between me and my roommate. Anyway. Also tried a couple drain products with no use then found something odd out. Lime Away seemed to work. I had pulled out the stopper for the drain while cleaning out the sink. (Stopper is broken on this sink unfortunately) Thanks to the sink draining VERY slowly due to the buildup of this grey slime it had some water in basin when I pulled the stopper out and some of the gunk came up and was floating around the water in bits.

To try and clean that and the rest of the sink up I sprayed a bit of Lime Away and noticed as I was wiping it down that it was starting to drain quicker. Sprayed some on the stopper (also had some slime on it) to test it and when sprayed then run under water it started coming off in chunks just from the water. (Had to scrape it off before). So I tried a few sprays right down the drain with water running and after about 3 sprays every 30 seconds for 2 minutes. The drain is working perfectly.

Not sure if it will work for anyone else but if you haven't found a solution. Figure it can't hurt.


Well, I tried all the suggested solutions and nothing helped. So I removed all the pipes and cleaned it out the hard way (paper towels, etc).

BUT, I was determined to prevent this from happening again, so I tried an experiment: for the last year I have stored a bottle of household disinfectant (Lysol, or generic/organic alternatives) conveniently near the sink. Now every time I use mouthwash at the sink, I chase it down with a few squirts of the disinfectant (and NO water). It has been nearly a year of daily use, and so far, no slime, no sluggish drain. I can live with that

UPDATE: Its been a few years, so I thought I would add an update. I found a preventative solution that has been working perfectly: NEVER USE WATER to rinse after spitting. I stopped water-rinsing a few years ago and haven't had to clean the drain since. (And I no longer use any disinfectant, either.) It was something about the moist environment that the water provided that led to the build-up. No water, no slime.

  • What about some hydrogen peroxide before you leave in the morning each day?
    – Evil Elf
    Commented Nov 25, 2013 at 13:47
  • for my mouth or the sink?
    – kmote
    Commented Nov 25, 2013 at 16:36
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    The sink. I use it to loosen up the film that accumulates on my shower track. It doesn't dissolve it like bleach, but letting it sit for a few minutes and then rinsing with water helps.
    – Evil Elf
    Commented Nov 25, 2013 at 20:21
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    In response to your update, so you spit into the sink basin and just leave it there, visible, until it dries? This would seem unpleasant if it contained any mucus. :-( Is that when you would use Lysol?
    – dougkramer
    Commented Feb 11, 2017 at 20:11
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    So do you just spit the mouthwash into the sink and let it dry? My wife would not accept this solution.
    – Evil Elf
    Commented Sep 27, 2017 at 13:20

These are the things I do with this problem.

The key is bleach as it will help kill the mold and bacteria. If your drain is heavily clogged with the black sludge then be prepared to do some work. Using a plunger with water and chlorine bleach will be time consuming and like others have mention will require cleaning the sink after each attempt with the plunger. The bleach will help kill the bacteria and loosen it up and clean the pipes and the sink. Then when you bring up the sludge to the sink, you clean it up. You may repeat this a lot of time depending on how long it has been building up. That's why I would suggest using bleach and hot water about once a month to keep the drain open.

A snake may work but if the pipes have a lot of sludge, it will just poke a hole through it and not really remove it all. Also when you bring that snake back up it will make a mess all over the sink, mirror, walls, etc. It will quickly grow back and you will have slow draining in the sink.

I have not tried them but cleaners that use enzymes may work as they are used to clear out bacteria in septic tanks and the principle behind them is sound.

I would avoid caustic type drain cleaners. They may work and it is easier to use but in the long run it is common knowledge that they will eventually damage your pipes resulting in costly repairs.

I think enzymes or baking soda, vinegar, hot water and a touch of bleach will do the job. The splash-less kind is easier to use. Just don't expect it to work the first or second time especially if the drain is clogged already. Once they are clear you just have to maintain it monthly but it should be a lot easier and you may not need to use the plunger.

Happy plunging everyone!

  • DO NOT MIX VINEGAR AND BLEACH Commented Feb 11 at 18:28

You may want to try using a foaming action drain cleaner. The foam will expand to fill the pipe. Here is a link to one example for Drano Dual-Force Foam.

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