My bathroom sink is very slow to drain -- I removed part of the pipe and there is massive build up of biofilm inside (presumably because of how it's not really tilted downwards enough).

How can I cause the biofilm to disintegrate and leave the pipe?

I have tried plunger the pipe which moves a little from near the drain but further down the pipe it is still very thick.

I've also tried pouring bleach down and leaving it for awhile, but it seems to make no difference. I can't really afford expensive cleaning stuff right now.

  • There is a commercial product Bio-Clean (statewidesupply.com/bioclean/index.html) that is specifically engineered to remove biodegradeable build-up on plumbing, septic tanks, etc. (disclaimer: I am in now way affiliated with them, but it comes recommended by professional plumbers and I have purchased and used it). It works well and if this is a systemic issue in your house, a worthy investment that is waaaay cheaper than plumber calls and MUCH more effective and safer on your pipes than Drain-O and similar detergenets.
    – A.S
    Mar 25, 2015 at 21:15

6 Answers 6


Or alternatively, just get some soda crystals, which are really inexpensive, (previously called washing soda) - heap it up in the plughole, boil a kettle, steadily pour the boiling water over the crystals till they've disappeared. Repeat an hour later, and as often as you like - I use 'em roughly once a month on kitchen and bathroom wastes. They won't clear hair build up though.

  • 1
    I ended up getting caustic soda, but it worked the same and left the pipes brilliantly clean. Now I just have to occasionally pull the hair catchy bit in the shower, and the sink drains fine :) Jan 5, 2018 at 16:35

Boiling water can hurt the pipes, so make it warm or just hot. Also, mixing a soapy water solution and pouring that down helps. Just follow some steps:

  • Use dish soap. This makes sure that the soap "kills" the grease and does not create scum.

- Use a plunger to make the blockage looser.

Additional info:

  • Using augurs or having someone else, they may also help.

  • Depending on the clog and your expertise - removing a part of the pipe may be the best method.


Vinegar, baking soda, and boiling water.

Start some water boiling. Pour 1/2 cup baking soda down your drain. Wait a few minutes. Pour 1/2 cup vinegar down the drain. Cover with a cloth (in case it is too reactive and bubbles out of the plug). Get the boiling water and pour it down the drain after the reaction between the baking soda and vinegar has died down.

Note: The pipes will sound like heck! They crack, sputter, and make all sorts of weird noises. This is normal. Be not afraid!

If you find more buildup after a while, you can try just pour boiling water down the drain, as it may clear it out with just water (we have a slow draining sink, and this helps tremendously).


The best thing to do is to remove the trap on your sink (it needs cleaned at LEAST once a year very well to keep things 'moving well') and then use a pair of gripping hemostats to poke up in the pipe, grab the hair (if there is any) and yank it out gently.

I just did this recently with our main bathroom's sink that had been giving us trouble for nearly a year.

You would not believe the GUNK that came out of it after putting numerous sinkfuls of near boiling water in it into the bucket I put under the steel sink pipe.

Surprisingly the spare bathroom that I use the most when I took the trap out and looked up in the steel pipe coming from the sink to the plastic trap? Whistle clean almost, I just had to rinse it out with hot water and our kitchen sinks sprayer.

Strange thing was the extremely hairy (literally) clog that was hanging on the pull-switch for the drain stopper. LONG LONG hairs. I'm talking 6 inches long at least. Even my mother does not let her hair get that long so I was going "Where the heck did this come from?"

Clog was so bad that the trap was nearly fully occluded and it was a wonder that anything could get through it.


Mixture of Dawn dish washing liquid and liquid bleach in a half gallon or gallon of water.

Pour in the drain and leave over night , several hours.

Once or twice a month and drains will be clean.

To make a point. Yes you must put more then one spoon full of the mixture in the drain.

You ask , are people so stupid as to put such a small amount of mixture in the drain??

Answer , Yes people are that stupid.

Notice the word Pour in the directions.

Yes is Ok to think about and experiment with the proportions of the mixture.

Known as evaluative thinking.

  • This may contain some useful information. It also contains rude comments which should be deleted . It needs to be formatted to make it more readable.
    – RedSonja
    Feb 18, 2019 at 14:30

I don't understand why nobody is recommending the products that are designed for this. Commercial drain cleaners (also called "drain openers") are either based on sodium hydroxide or sulfuric acid. Don't use them together, as they would simply neutralize each other and risk melting your pipes during the process.

You aren't supposed to use sulfuric acid on steel pipes, but it's fine for plastic. The black liquid drain cleaners are usually sulfuric acid. It's stronger stuff, and makes worse fumes than the sodium hydroxide. It's cheaper as well. There might be corrosion inhibitors added, to spare your pipes. And don't use the hydroxide when cleaning up fats/oils, as some will be turned into a soap which is even more solid than the original form. Both classes or drain cleaner can dissolve organic matter like hair, paper, and flesh.

You pour a product into the drain. If the product is powder/flakes, add the minimum amount of hot water you can add to make it dissolve. Wait the amount of time the packaging says to wait, then flush the pipes out with water. Hot water, if that's what the product says to use.

It won't hurt you much to get these products on your hands if you quickly wash it off, but eye protection is mandatory, as you don't want to risk your vision.

If you find the right product, it will cost $2 or less, but I couldn't tell you where to look. A supermarket or hardware store will have a branded drain cleaning product, unbranded might be what you need to look for if you are short on funds.

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