What Is the Pink Slime in My Bathroom?

If you’ve ever noticed pink slime or residue form around your sink or shower, along the rim of your toilet, or even inside your pet’s water dish, you’re not alone. In fact, it’s a very common—but easily misunderstood—issue.

The biggest misconception surrounding pink slime is that it’s caused by a mold. It’s not. What is it? We'll uncover that and more below.

Table of Contents: 

• What Causes Pink Slime?
• How Do I Get Rid of Pink Slime?
• Is Pink Slime Dangerous?
• What's the Takeaway?

What Is the Pink Slime in My Bathroom? 

Pink slime is most frequently caused by an airborne bacterium called Serratia marcescens.[1] Found worldwide, S. marcescens  thrives particularly well in damp environments. The bacteria grow well on materials containing phosphorus or fatty substances (such as feces in your toilet bowl, or soap residue in your shower), making your bathroom its ideal environment. 

This means you're not actually dealing with a water contaminant, but an air quality contaminant. Because Serratia marcescens forms a pink/red biofilm at room temperature, it is also easily confused as an iron-related water quality issue in the water.

This leads us to another common misconception: water treatment equipment can help. Serratia marcescens transports by air, not by water, so water filters won’t likely help solve the problem.

So if it’s in the air, how do I get rid of Serratia marcescens?

How Do I Get Rid of Serratia marcescens? 

When it comes to pink slime and S. marcescens, the name of the game is “management,” rather than elimination. Unfortunately, no matter how much you clean, the plentiful supply of this airborne bacteria makes getting rid of its pink slime very difficult.

You can take the following steps to reduce the amount of pink slime that appears in your bathroom:

1. Ventilate the room during and after a shower for at least 30 minutes
2. Use an after-shower spray or squeegee to remove soap residue in your shower and tub
3. Limit the amount of moisture and soap scum you leave on surfaces

If you already have pink slime, you can deal with it this way:

1. Make a one-part vinegar and one-part water solution.
2. Spray the mixture onto the pink slime that has already left its mark. 
3. Let soak for 10 minutes.
4. Scrub away the bacteria. 

You can also use this bleach solution.[2]  

Note: It’s very likely that the pink slime will re-grow. It may be only just a matter of weeks before it reappears, but it probably will. 

A couple of other things to note: Serratia bacteria will not survive as well in chlorinated drinking water. However, because chlorine is a volatile compound, if water stands long enough for residual chlorine to dissipate (i.e., in a toilet or on a shower curtain), pink slime may develop. 

People who remove chlorine from their water by the use of a whole-house activated carbon filter are more likely to encounter pink slime. 

Additionally, the problem tends to occur more often in the summer months, when temperatures and humidity are higher. This holds even more true if windows are left open for extended periods of time. Because Serratia marcescens can be stirred up during yardwork or construction, take extra precautions to keep windows closed during these periods. 

Is Serratia marcescens Dangerous?

While pink, slimy rings in your bathroom are almost impossible to eliminate completely, they are harmless (unless you are in extremely poor health)!

Outside of very rare cases, Serratia marcescens poses almost no health risks.[3]