Black Sludge: What It Is, Why It Smells So Foul, And What It Is Doing In Your Drain

23 November 2018
 Categories: , Blog


Does your bathroom drain frequently smell like a sewer? When you take apart the pipes underneath, does the trap contain a black sludge? Nasty, is it not? You may be wondering a lot about that black sludge. You may even be worried about it. Here is more about black sludge in your drain, why it smells so foul, and exactly what it is.

What the Black Sludge Is 

The black sludge is a mess of things. There is hair, skin, and soap residue involved. There is also a lot of bacteria that you washed off your hands. Quite often, depending on how the pipes under the sink are connected, sewage may find its way backward through the drain pipe and into the trap. That whole mess sits in the trap and just rots and stinks into a sludge that will not budge. 

Why It Smells So Foul

It is rotting. Hair and skin are organic, so they rot. Soap residue acts as a glue, so it holds all of that rotting material together. Then there is the occasional backflow of raw sewage, which the trap prevents from flowing upward into your sink. Raw sewage is bad enough without the rest of that sitting there and getting more rotten by the minute. Eventually, you will be able to just lean over the sink and smell that stink without doing anything else. 

What It Is Doing in Your Drain

The black sludge is stuck. It cannot move beyond the trap, and it cannot move back up into the sink either. A sink auger can help pull some of it out and help clear the drain. A powerful plunger can help pull some of it back up into the sink, too. However, with as black and as foul as it is, you really probably do not want to do that. Instead, call a professional plumber, who will have a few drain cleaning tricks up his/her sleeve.

Drain Cleaning With Black Sludge

The plumber will do one of three things to help clean out your drain. One, he/she will use a powerful flushing tool to force the black sludge out of the trap and through the pipe that is connected to the main drain of your house. Two, he/she will use a bio cleaner that eats most of the black sludge and makes it easier to rinse out of the trap and down the drain. Finally, three, the plumber will remove your trap directly and flush and clean it out thoroughly before flushing the pipe after the trap and reconnecting everything.