How to Remove Black Sludge from Sink Drain Fast!

What is the Black Stuff in My Sink Drain?

Are you seeing black gunk coming up from your sink drain. I know how gross that is and I will tell you where it is coming from and how you can get rid of it.

Black sludge in your sink drain is caused by bacteria growing in the biofilm inside the drainpipe. The biofilm is made up of hair, toothpaste, body cells, shampoo, oils, grease and other waste. Layers of biofilm cling on the drainpipe creating a perfect environment for bacteria to grow which turns them black.


When you use a sink, most of the waste will flow down the drain line bust some will stick inside the interior surface of the pipes. That is the waste that creates the biofilm which in turn attracts bacteria and as the bacteria grows the film turns black.

Apart from looking and actually feeling gross, the black biofilm from your sink drain can result in a foul smell or lead to health problems. They include Salmonella, Shigella and E. Coli.

The black gunk in sink drains affects bathroom sink drains more than kitchen sink drains. This is caused by the design of the bathroom sink drain which allows more waste to stick inside the drain line unlike in kitchen sink drain.

You see, bathroom sink drains have a popup stopper whose mechanism is usually inside the drain line. The popup mechanism gives room for hair, body cells, soap scum and other wastes to stick and hence faster buildup of the biofilm.

To get rid of black sludge in a sink drain, pour one cup of baking soda followed by another cup of vinegar then wait for 15 minutes when you will dump a gallon of hot water to flush down the gunk. You can also remove the popup stopper and P-trap and clean them physically then connect them back.

What you want to do is avoid using harsh chemicals to remove the black sludge. While the harsh chemicals will without a doubt get rid of it, they are bad for the environment, will damage your drain lines and kill the good bacteria for folks on a septic system.

To prevent the black sludge from forming in your sink drains or any other drains, clean your drains using baking soda and vinegar regularly. Pouring boiling or hot water down the drain is also very effectively in melting and flushing down the gunk.

How Do I Get Rid of Black Sludge in My Sink?

black sludge in sink

Now let us look at how to get rid of the black slime from your sink. There are actually several ways to do it but we will go systematically starting from the easiest one.

1. Snake the Sink Drain

As I had already mentioned, bathroom sink drains are usually clogged by hair. Strands of hair stick together inside the drain line forming balls especially after combining with oils, shampoo and soap scum.

The good thing is that snaking a sink drain is very easy. Actually, you don’t need to snake it using the usual drain auger but by using a hair sink removal tool.

A sink drain hair removal tool is a flexible plastic tool (sometimes called a zip tool) with hooks on both sides that you just stick inside the drain line, twist it then pull it with the hair.


These tools are safe to use unlike the metallic ones since they can’t damage the drain line.

If you do not have this tool, grab a wire coat hanger and straighten it then use pliers to make a hook on one of its end. Use it to fish out hair gunk from the drain and when you are done blast hot water down the drain to flush the little debris still left inside.

2. Use Baking Soda and Vinegar

Baking soda and vinegar are very effective in unclogging drains. They react together in a fizzing reaction and in the process break down the gunk.

Vinegar is a weak acid while baking soda is a base so they will neutralize after the reaction. If you do not have baking soda then borax will be a fantastic replacement.

Both of them are also safe for your plumbing since there is no heat generated which can deform pipes unlike chemical drain cleaners. They are also septic-safe and will therefore not kill the good bacteria inside your septic tank.

Here is how to remove black gunk from a sink drain using baking soda and vinegar:

  • Start by boiling about 1 gallon of water.
  • Pout 1 cup of baking soda in the sink.
  • Slowly add another cup of vinegar down the sink drain
  • Wait for about 15 minutes for the mixture to work out its magic. This also gives the water time to boil.
  • Dump the boiling water in the sink.

While baking soda and vinegar will break down the black gunk into tiny pieces, the hot water will melt any gunk still sticking on the drain line and flush it down leaving the drain line clean.

3. Remove and Clean the Pop-up Stopper Assembly.


Before using the baking soda and vinegar, you may decide to remove and clean the pop-up stopper assembly. This is where most of the biofilm will be trapped.

The popup stopper assembly is made up of the following:

  • Lift rod
  • Pivot rod
  • Plug
  • stopper cap

The lift rod is that you pull from the top but it extends underneath the sink where it is connected to the pivot rod.  There are several holes on the lift rod for connecting the pivot rod at different heights.

The pivot rod goes inside the drain line where it is hooked to the stopper plug. From the top of the sink, the stopper cap is screwed on the plug.

  • Duck under the sink and remove stuff stored there to give yourself enough space to work with.
  • Start by noting and marking the exact hole on the lift rod where the pivot rod is connected to.
  • Disconnect the pivot rod from the lift rod using pliers.
  • Loosen the coupling connecting the pivot rod to the drain line with your bare hand. Only us a wrench if it is too tight.
  • Pull out the pivot rod.
  • Now that the stopper plug is free, remove it from the top of the sink.
  • Drop it inside a bowl with warm soapy water and clean it using an old toothbrush.

Move to the next step.

4. Remove and Clean the P-trap


A P-trap is the U-shaped part of the sink drain line.  It serves 2 purposes:

  • It holds a little amount of water at all times preventing sewer gases from coming up through it.
  • It traps potential drain clogs preventing them from clogging the drain line farther away.

The shape of the P-trap allows it to trap lots of gunk (hair, soap scum, oils, shampoo etc.) which is what forms the black biofilm.

By removing and cleaning the P-trap, you will have removed most of the black sludge from the sink drain. Here is how to do it:

  • Place a small bucket or pan under P-trap. This will prevent the water already inside it from spilling on the floor.
  • Disconnect the P-trap. Most of the time the connections will be hand-tight but if they are not you can always use a wrench.
  • Check the inside of the P-trap for the black gunk.
  • Tap it against a hard surface t remove as much of it as possible before dropping it in a bowl of warm soapy water to clean it.
  • You can also insert a wet rag in the vertical section of the drain line to clean it as well.
  • When the P-trap is clean connect it back.

Connect the pop-up stopper assembly as well.

  • Start by pushing the plug inside the sink drain opening.
  • Insert the pivot rod through the opening on the drain line and hook it to the plug.
  • Screw in the pivot rod coupling.
  • Connect the pivot rod to the lift rod on the exact hole you marked.


To clean the drain line and get rid of any lingering smells, pour half a cup of baking soda followed by another half cup of vinegar then wait for 15 minutes.

Blast hot water through the sink drain to flush out any debris still in the drain line. Do this frequently to prevent the black sludge from forming inside the sink drain.

In rare occasions, the black gunk can be caused by a clogged plumbing vent. Check out this post to learn how to unclog a plumbing vent.

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