What’s That Black Slime on My Plumbing Fixtures?

You pride yourself on a spotless bathroom and kitchen. But perhaps lately, you’ve started noticing black, slimy buildup on your fixtures—faucets, shower heads, toilets, sinks, you name it. Eager to restore their gleaming shine, you grabbed the strongest cleaner you could find. The residue went away for a time, but there it was again: that nasty, stubborn slime.

If this has been your experience, you’re not alone. Many homeowners report seeing this disgusting gunk on their fixtures—even those with stringent cleaning routines. So, before you start scrubbing everything from top to bottom, let’s figure out what could be causing these strange black deposits, their potential health effects, and how to get rid of them.

What is the Black Slime, and What Causes It?

That slimy black gunk on your fixtures is likely oxidized manganese, a metal often found in trace amounts alongside iron in drinking water. Water can pick up both as it travels through soil and rock, but iron can also come from corroded pipes and plumbing made from galvanized steel.

The minerals combine with oxygen when the water is exposed to air—like on your kitchen faucet aerator or shower head. Oxidized iron forms yellowish or reddish deposits, which we know as rust, while oxidized manganese appears brown or black.

When you pour the water, these particles can settle out, possibly giving it a red, brown, or black tint. But sometimes, certain bacteria may feed on the oxidized manganese and produce a distinct black gooey substance. You’ll likely see an orange-brown slime if it’s iron bacteria.

This phenomenon is widespread in areas with high levels of iron and manganese in the water, such as regions relying on well water.

Related: How to Remove Iron Bacteria from Well Water

Is Black Slime on Fixtures Harmful?

Much like iron, a little manganese in your water shouldn’t be a problem. Trace amounts of both in your diet help maintain good health. Manganese, in particular, provides many health benefits in low doses. But that doesn’t mean ingesting more is necessarily better. The opposite may be true.

According to the Minnesota Department of Health, “Children and adults who drink water with high levels of manganese for a long time may have problems with memory, attention, and motor skills. Infants (babies under one-year-old) may develop learning and behavior problems if they drink water with too much manganese in it.”

As if that wasn’t bad enough, a study published in the journal Frontiers of Microbiology suggests that ingesting too much of certain metals, such as manganese and iron (from drinking water), “may cause mild symptoms such as anorexia, weakness, apathy, and learning and understanding problems, but can also cause serious diseases such as Parkinson’s or Alzheimer’s disease.”

Too much of these metals can also make water taste bitter and stain toilets, sinks, and laundry. That’s why the Environmental Protection Agency (EPA) recommends that iron and manganese shouldn’t exceed 0.3 milligrams per liter (mg/L) and 0.05 mg/L, respectively, as these guidelines help prevent bad taste and staining.

As for manganese bacteria, they are not considered dangerous. They are not known to present a health risk. They can, however, cause aesthetic issues in water, like metallic taste and smell and stains on tubs/showers, toilets, plumbing fixtures, and laundry.

Who’s More at Risk of Seeing Black Slime on Their Fixtures?

Black slime can appear on your fixtures and surfaces regardless of your water source. However, if your water comes from a private well, it likely contains more manganese than those on city water—hence a higher chance of seeing those black, slimy deposits. That’s because the EPA doesn’t regulate private wells. Private well owners are responsible for testing their water and treating it if necessary.

Learn more: Buying a House with a Well System? Here’s Everything You Need to Know

How Do I Know If It’s Manganese Bacteria Causing the Black Gunk?

Aside from manganese bacteria, rubber seals in your water heater and corroded pipes can also cause black gunk on your fixtures. There’s also a slight chance you’re seeing mold, though this is rarely the case. Mold typically grows in dark, damp places with little water movement. So, it’s very unlikely that mold is growing on your faucet aerators—unless they haven’t been used for a long time. The only surefire way to know what’s in your water is to have it tested, preferably by a certified laboratory.

While at-home tests are usually more affordable and offer some accuracy, laboratory testing is often more thorough and precise. The latter can reveal the extent of the contamination problem and detect other contamination issues. It can also measure other vital parameters like hardness level, pH (acidity or alkalinity), Total Dissolved Solids (TDS), turbidity, etc.

ETR Laboratories offers quality and reliable water test kits with specific instructions for collecting and submitting the water sample. The results are usually reported in a couple of days. Plus, once they’ve sent out the results, they offer free follow-up phone calls with their experts to ensure you know how to improve your water quality and remove harmful contaminants.

Learn more: 10 Common Problems a Water Test Can Detect in Tap Water

Is Manganese in Drinking Water Regulated?

Unfortunately, the government doesn’t regulate how much manganese can be in your drinking water. The EPA has set some voluntary safety standards and health guidelines related to manganese. However, as “voluntary” suggests, they aren’t legally enforced rules water utilities must follow.

As part of their guidelines, the EPA suggests keeping manganese in water under 0.05 milligrams per liter to avoid issues like black stains and metallic tastes. They’ve also advised extra caution for infants, recommending iron levels below 0.3 mg/L. While they don’t require testing or set concrete limits, the EPA has provided useful benchmarks to guide local decision-makers and water utilities to address potential iron and manganese contamination.

Understandably, you may feel worried and uncertain knowing the guidelines are just recommendations. When it comes to drinking water safety, stricter regulation often brings people peace of mind. So, let’s explore some simple and practical methods to remove black stains from your fixtures and prevent manganese contamination in your water supply.

Related: Why Federal Regulations Are Vital for Clean Drinking Water, But Not Sufficient | EPA Proposes First-Ever Federal Regulations for PFAS in Drinking Water

How to Get Rid of Black Slime on Fixtures

Like most people, you probably don’t want that nasty black gunk anywhere near your home. But if it’s already taken up residence on different fixtures and surfaces, follow this straightforward process to get them sparkling clean again.

How to Remove Black Slime from Faucets

  • First, check the manufacturer’s instructions to know what cleaners will be safe and effective on the specific finish of your faucets. Some finishes, like oil-rubbed bronze or brass, are easily damaged.
  • For most faucet materials, scrub gently with dish soap and a damp cleaning cloth.
  • If that doesn’t cut through the grime, spray a “less visible” spot on the faucet with a 50/50 vinegar and water solution. Let it sit briefly before wiping it clean. If it works, spray it all over the faucet.
  • To tackle hard-to-reach areas, use an old toothbrush and gently scrub away the black buildup with the cleaning solution.
  • A paste of baking soda and water may also help lift stubborn black stains. Apply and let it sit before scrubbing and rinsing it clean.

How to Remove Black Slime from Sinks

  • For bathroom sinks, spray the basin with a 50/50 vinegar and water solution or another general-purpose cleaner.
  • For stubborn gunk, make a paste of baking soda and water. Apply the paste and let it bubble away the sludge before rinsing.

How to Remove Black Slime from Shower heads

  • Fill a plastic bag with undiluted white vinegar. Secure it over the shower head with a rubber band. Let the shower head soak in it for one hour before removing and flushing it clean.
  • Clean oil-rubbed bronze or antique brass fixtures with water to avoid damage. Test any specialty cleaning products on a small spot first.

How to Remove Black Slime from Toilets

  • Use a general-purpose cleaner or soapy water mix for wiping down the toilet’s outer surfaces. Rinse and dry thoroughly.
  • Clean the toilet seat with mild dish soap. Sanitize by scrubbing the bowl interior with bleach or antibacterial toilet cleaner.

Related: How to Remove Hard Water Stains from Your Plumbing Fixtures: A Detailed Guide | What Causes Pink Bathroom Slime, and How Do I Remove It?

How to Remove Oxidized Iron and Manganese from Drinking Water

As explained earlier, iron and manganese bacteria feed off oxidized forms of the metals to create a slimy buildup on your fixtures. Therefore, the first step should be to cut off their food supply. That means eliminating the oxidized iron and manganese from the water supply.

The best way to achieve this is to install an oxidizing filter, such as the Springwell WS1 Whole House Well Water Filter System. This system uses a powerful Air Injection Oxidizer to remove iron, manganese, and hydrogen sulfide from well water.

The system maintains an “air pocket” at the top of the tank while in service. Iron, sulfur, and manganese oxidize as water passes through the air pocket. The oxidized contaminants are then filtered out of the water.

The filter uses a patented piston in the control valve to perform the whole oxidation process in one tank, keeping maintenance costs and downtime to a minimum. Furthermore, the system can remove up to 7 parts per million (PPM) of iron and 1 PPM of manganese and requires no maintenance. The regeneration process also adds a fresh air pocket to the system, which removes any sulfur (rotten egg) smell in the water.

Related: How to Get Rid of Rotten Egg Smell in Water

How to Remove Iron and Manganese Bacteria from Your Water Supply

While cleaning your fixtures regularly or flushing the main supply line can be effective, these are only temporary fixes that will cost you time and money but won’t solve the issue. Unless you address the root cause, it’s only a matter of time before the black slime returns.

If you’re confident iron or manganese bacteria is the issue (as confirmed by a water test), there are various steps you can take to prevent the problem.

Shock Chlorination

Shock chlorination involves adding a relatively high chlorine concentration (about 200 ppm) to the water to disinfect it. As you probably know, chlorine is a popular chemical disinfectant used in most public water systems in America.

Chlorine is toxic to coliform bacteria and other waterborne microbes like parasites, viruses, fungi, molds, and algae. These microbes commonly grow in water supply reservoirs, well casings, plumbing lines, and storage tanks. However, iron and manganese bacteria are more chlorine-resistant because the slime they secrete usually absorbs some chlorine before it reaches the bacteria.

With that in mind, we recommend adding a higher chlorine concentration (about 500 ppm) to address these bacteria problems. We also suggest shock-chlorinating your well about 2-3 times yearly if you are experiencing bacteria contamination and don’t have an automatic chlorinator or chemical injection system. Without continuously injecting disinfectant into the water, the iron and manganese bacteria will likely resurface and continue to cause problems in your water.

Check out our comprehensive, step-by-step guide on how to shock-chlorinate your well.

Chemical Injection

Chemical injection systems automatically feed chlorine or other chemical disinfectant into your water supply to kill microbes that can cause the black gunk on your fixtures. It’s way more efficient and convenient than having to shock-chlorinate your well manually.

The chlorine is stored in a solution tank, pumped into the pipeline under pressure, and mixed with the well water in a contact tank until needed. This gives the water enough contact time with the chlorine to eliminate even more microbial contaminants. The pumps adjust how much disinfectant they use based on how quickly your water flows. This helps maintain a precise residual.

Of course, you don’t want to drink or shower with chlorinated water. It can burn your nose and eyes and damage your clothes, surfaces, and who knows what else over time. That’s why we recommend adding our Whole-House Water Filter to our Well Water Chemical Injection System after it’s installed.

The whole-house system helps remove/reduce chlorine in the water once it finishes its disinfection. The injector system even has a timer feature, allowing regular “shock doses” of chlorine to prevent iron and manganese bacteria regrowth. The result? Clean, chemical-free water for showering, drinking, and all your household needs.

What Methods Won’t Permanently Fix the Black Slime Issue?

Google “how to remove black slime from fixtures,” and you’ll be bombarded with well-meaning recommendations that won’t solve the underlying issue—iron and manganese in your water supply. Filtering the offending minerals is the only way to get a permanent fix. Once the iron and manganese are gone, the black gunk will most likely be a thing of the past!

So, if you see any of the following tips on or offline, be careful, as they are only temporary solutions:

  • Clean the affected areas regularly with chemicals or natural remedies.
  • Flush the main water supply line.
  • Replace your pipes.
  • Use toilet bowl cleaner (which may damage the rubber seals and valves in the tank).
  • Install a water softener or a whole-house filter that lacks the required filtering capacity.

Final Thoughts

There you have it. The black, slimy stuff on your fixtures is no longer a mystery. While alarming to find, it shouldn’t leave you worried or fearful. Yes, it can be a little stinky and make your home appear unclean, but the black gunk itself isn’t a health hazard.

If you have black slime on your fixtures, test your water to see if it contains iron, manganese, or both. While you can clean your faucets, showerheads, sinks, and other areas to remove the sludge, install a whole-house oxidizing filter system to remove the metals and a chemical injection system to destroy any bacteria in the water. You can also follow our shock chlorination guide to learn how to disinfect your well water system.

Follow these tips, and you’ll be on your way to having clean water throughout your house and no longer being bothered by black, nasty-looking stains or slime.