Encountering odd-looking black residue in your bathtub can be concerning, to say the least.
But this is actually quite a common occurrence that many homeowners have to deal with at some point.
While a small amount of sediment deposit isn’t anything to worry about, if you consistently spot black, greasy deposits left in your bathtub, it may indicate a deeper problem with your home’s water system that needs addressing.
To help you with this issue, I’m going to list all the primary reasons why this black residue might occur and give you an easy-to-follow guide on how to get each problem fixed so you can have a clean bathing experience without dealing with unsightly black residue.
What Causes Black Residue In My Bathtub?
There are quite a few potential causes that will cause black residue to form in your bathtub.
But by taking a closer look at the deposits, we can quickly identify where it’s come from and get a good idea of how to fix the problem.
1. Mold or Mildew
Mold and mildew usually grow in damp, humid and warm spots.
This makes the pipes and faucets that supply water to the bathtub a prime candidate for fostering mold growth.
Mold and mildew will usually adhere to the walls of the plumbing quite well, so you may not notice it at first.
But as it grows and starts to break off, it will then be left in your bathtub.
Needless to say, this will make anyone using the bath quite uncomfortable, but you can fix this problem by cleaning out the plumbing of any mold or bacteria buildup.
2. Mineral Deposits
Water naturally contains particular minerals such as manganese or iron, but usually in low amounts.
However, if you live in what’s considered a ‘hard water’ area, the mineral content in the water may be higher than normal.
This high mineral water can leave black stains and buildups in your bathtub over time.
While this doesn’t present an immediate health risk, the deposits can be unsightly and in rare cases, they can affect your skin.
These deposits can easily be cleaned off with some vinegar and scrubbing, but if you want a more permanent solution, you may wish to consider installing a water softener.
3. Water Filter Carbon
Some homes utilize carbon filters designed to trap contaminants inside tiny pores of activated carbon.
Like most filters, these small pores will eventually get clogged up and stop performing effectively.
This will then cause the water from your faucet to contain impurities that may leave black spots in your bathtub.
Not only that, but if the carbon filter is not replaced for a long time, it may start to degrade, causing small bits of carbon to release from the filter and make their way into the water supply.
So it’s a good idea to replace the carbon filter at regular intervals to keep the black deposits down to a minimum.
4. Pipe Rust Specs
Many water pipes, particularly those in older homes, may contain iron oxide, which tends to react with the minerals in the water supply, forming dark-colored stains on your bathtub.
Not only does this indicate that your pipes might be rusty and needs to be dealt with asap before it leads to a more serious plumbing issue, but once the black residue forms inside the bathtub, it can be a real pain to clean off.
5. Corroded Rubber Components
Many plumbing systems use rubber components for things such as gaskets.
As this rubber ages, it has a tendency to lose its rubberized quality and turn hard and brittle.
This now brittle rubber may crumble or chip off, causing little black bits of old rubber to get into the water supply and be left in your bathtub after it’s drained.
The rubber components inside your plumbing system will need to be inspected and any old or decaying rubber components will need to be replaced.
6. Soap Accumulation
Even if you regularly wash your bathtub, over time, soap can accumulate and form a thick layer on your bathtub.
This may take on a murky brown or, eventually, if it’s not cleaned, will turn black.
You’ll need to use some special cleaning solutions and scraping methods to remove the soap scum accumulation and ensure you keep up with regular maintenance in the future to stop it from coming back.
7. Corroded Water Heater Anode Rod
Your heater will have an anode rod inside of it, usually made from magnesium or aluminum and is designed to protect the water heater from water corrosion.
However, over a long period, this rod may start to corrode itself, creating a black residue that will flow through into your bathtub.
Ideally, the anode rod should be replaced every few years, so if you haven’t had this inspected in a long time, now is a good time to do it.
8. Sand or Silt in the Water
If you live in an area where the water comes from a well, small pieces of sand or sediment may be picked up along with the water.
Ideally, your plumbing system will utilize a sediment filter to assist in removing these deposits.
But if this filter has stopped functioning for some reason, then this sand will make its way into the water supply and end up being deposited in your bathtub.
You must have your water system inspected and your sediment filter fixed accordingly.
How To Remove Black Residue In Your Bathtub?
Now that you better understand what this black residue is and where it comes from let’s walk through how to get each of these problems fixed so you can remove the black residue from being deposited in your bathtub permanently.
1. Kill and Clean Up Mold and Mildew
Small amounts of mold growth can be easily addressed by yourself with a few simple cleaning products and some elbow grease.
However, in rare circumstances, a more serious underlying issue may contribute to mold growth, such as a cracked pipe, leak or lack of bathroom ventilation; you may need to contact a plumber for extra help.
- Start by ensuring you have adequate protective gear, gloves, eye protection and a breathing mask will help protect you as you clean out the mold.
- Get a good mold cleaning solution, white vinegar works exceptionally well, but things like bleach or a purpose-built anti-mold product also work. Using these, scrub the affected areas in the bathtub down.
- Purchase a chemical cleaner designed for your pipes and, following the manufacturer’s instructions, apply them to the pipes and drains of your bathroom to kill off the mold you cannot reach by hand.
- Set your environment so it’s conducive to not fostering mold growth; this may be by increasing the ventilation in your bathroom or using a dehumidifier to dissuade mold growth.
2. Clean Off the Mineral Deposits
If mineral deposits leave black particles in your bathtub, the first thing to do is clean off the current buildup.
The easiest way to do this is using a cleaning solution of equal parts vinegar and water.
Apply it to the black specks and let it sit for a few minutes to help break the deposits down.
Scrub it thoroughly with a brush or sponge to loosen it, then rinse it thoroughly with water; if it’s particularly stuck, you may need to use a commercial descaler.
Now that the buildup is addressed, you need to stop it from coming back in the future.
You can do this by installing a water softener in your home, which will help to filter out the mineral deposits in the water.
3. Replace the Carbon Water Filter
Once the carbon filter gets old, it will allow deposits to pass through into your bathtub, so you’ll need to swap the filter out with a new one.
- First, turn off the water supply at the shutoff valve.
- Remove the old filter; this process will vary depending on the make and model of water filter you are using. We recommend referring to your user manual if you are not sure.
- Install the new filter in its place, ensuring it’s properly seated and secured in place.
- Once the new filter is installed, you’ll need to flush it through for a few minutes to ensure it will work properly.
4. Address the Rusty Bathroom Pipes
While there are some DIY solutions to cleaning out rusty pipes, including using a cleaning solution of equal parts water and vinegar or baking soda, pouring this down the pipes and then rinsing it through with water.
However, if the rust buildup is more serious, it’s a better idea to call a plumber who can better assess the situation and recommend the best course of action based on the severity of the issue.
5. Replace Any Corroded Rubber Components
Once rubber components start to crumble, they are of no use anymore.
So you’ll need to inspect the components in your home’s plumbing system, such as gaskets and replace any old, cracked or crumbling with new ones.
If you are not confident in doing this yourself, then once again, it’s a good idea to contact a plumber.
6. Clean Off the Soap Scum
Fortunately, soap scum is easy to address as it’s localized to the bathtub.
One of the best solutions to break down soap buildup is by making a cleaning solution of equal parts dish soap and vinegar.
Apply this solution liberally over the bathtub and let it sit for 30 minutes to break down the buildup.
Scrub the surface with a brush and then rinse it away with water; if you don’t have vinegar to hand, you can also use a baking soda and water mixture using the same method.
7. Flush the Water Heater
Short of calling a plumber to install a new water heater, you can also address the issue by flushing your water heater to remove the sediment accumulation on the anode rod.
To do this, you can attach a garden hose to the valve located at the bottom of the water heater.
You can then drain the water into a bucket to remove the sediment.
8. Install a Sediment Filter
If sand or sediment is making its way into the water supply, it’s crucial to identify the source of where this is coming from.
If there is a more serious issue, you will need to contact a plumber to further assess the situation.
However, if the issue is relatively minor, you can install a sediment filter to help remove small amounts of debris and keep your water clean.
If this seems like a desirable option, then you should consult a plumber to help determine the best location for the filter, suggest a good model and assist you with the installation.
Paul Wilson is a highly skilled plumber with over ten years of experience in the industry. He holds an IDPH license and takes pride in his ability to tackle many plumbing issues and successfully complete even the most challenging projects.
