How to Remove All Types of Pool Stains (Causes & Treatment)



As a conscientious pool owner, you’ve always been systematic and disciplined with your pool care regimen; cleaning the pool, balancing the water, and adding chemicals when needed, etc.

Nevertheless, stains have magically sprung up out-of-the-blue and you don’t know where to turn. Have no fear. Pool stains have causes and solutions and we’ll get to the bottom of it.

What Causes Pool Stains?

In order to properly manage and remove a mysterious pool stain, you first have to know what caused it. Once you know that, you can grab the right stuff to clean it correctly.

Pool stains come in two flavors — ew. Actually, that sounds pretty gross. Let’s say: causes. The two main reasons for pool stains can be traced back to either metal or organic origins.

Metal Stains

There are several reasons why you might find metal staining in your pool. Your water source is the first place to look. If you use well water or if your local water source has lots of metals dissolved it in, the metals can come out of solution and form stains on the bottom or sides of the pool. 

The next is your metallic pool equipment. Perhaps some of your pipes have corroded and are sloughing off into your pool water. Rust is included in this category too. If any of your pool equipment is old and has started to rust, chances are you’ll see evidence in the form of staining.

Organic Stains

The other possible explanation for your mysterious pool stains is an organic culprit. These include things like leaves, dirt, berries, algae, oils, and other plant matter. Organic stains are a bit easier to track down because you’ll probably notice the actual leaves, dirt, or berries lurking at the bottom of your pool too.

Now that you know the causes, let’s investigate a bit further by looking at the color(s) of the stain, which will also tell you the source of the stain.

Identify the Color(s) to Identify the Stain

If you gaze into your pool and notice a stain at the bottom or along the sidewall, don’t panic. The first step is to take a closer look and see if you can make out the colors of the stain.

Once you determine the primary colors of the stain, you can figure out how to fix the problem. 

Red/Blue Stains

Normally, the cause of this discoloration in your pool is berries. If you have any berry trees or bushes near the pool, trim them back and make sure to clear all of the berry debris out of your pool water.

Green/Brown Stains

This color stain can be attributed to organic debris decomposing in your pool. Leaves, dirt, or other plant matter can leave greenish-brown stains when left to decompose in the pool for too long.

Green/Blue/Black Stains

If you’ve determined that organic matter is not to blame, this kind of discoloration is most likely due to an overabundance of copper in your pool water. Copper staining can be caused either by too much copper in your water source (well water, etc.) or it can be a result of corroded copper piping in your pool’s plumbing.

Green/Brown/Red Stains

When on the hunt for the cause of pool stains, a reddish color, perhaps mixed with brown or green, is usually evidence of an excess of iron in the pool. Take a look around for any rusted metal, such as a fence, ladder, or other pool equipment that may be rusting to find the culprit.

Brown and/or Purple Stains

A purplish stain you say? Well, that one is much easier to figure out. Whenever you see purple staining in the water, other than berries, the most likely cause is a surplus of manganese in the water supply. Manganese is typically found in high levels in well water but is also in municipal water, depending on where you live. 

Test Your Theory

Now, armed with the possible causes of your multi-colored pool stains, you can move on to the next step of testing your theories. Only when you’ve confirmed the cause can you move on to treating (and preventing) those unsightly pool stains. 

Just as there are different kinds of pool stains with their own nefarious causes, so too are there different tests to determine the causes. Let’s take a look at how to test for each. 

Testing for Organic Stains

To find out if your pool stain is organic, the test is easy. Simply apply a bit of granular chlorine directly to the stain to see how it reacts. If the stain is truly organic, it should dissipate quickly and without fanfare.

Testing for Metal Stains

You may think that the cleaning power of chlorine knows no bounds and tossing it onto every stain will do the trick. Sorry to burst your bubble, but unfortunately, chlorine has little to no effect on metal stains at all. 

For this type of staining, we need to call upon another weapon in the pool care arsenal: ascorbic acid (or vitamin C). If you think that your pool stain has a metallic culprit, simply apply some ascorbic acid powder directly to the stain. If the stain lightens or comes off with this application, you can bet it was caused by metals.

How to Get Rid of Pool Stains

Now that you have an idea of what caused your obnoxious pool stains, pool stain removal is the next step.

Unfortunately, there isn’t a one-size-fits-all, all-purpose cleaner for pool stains.

Removing Metal Pool Stains

Let’s get the tricky one out of the way first. Metal stains can be a bit more difficult to get rid of than organic stains, but not impossible. Simply follow the step by step process to get your pool back to its stain-free former glory.

Step #1 Test the Pool Water for Metals: If you’re determined that metals are your stubborn-stain culprits, the next step is to find out what kind of metals you’re dealing with. The best way to find out is to grab a water sample and take it into a local pool supply store to get the low-down. 

Step #2 Get the Right Metal Remover: Let’s refer back to the earlier section where we discussed the different colors of metal stains you might find in your pool. Depending on the color of the stain (and the report from the pool water test you got), you can purchase the right metal stain cleaner for your particular stain.

If your stains are caused by an excess of iron in the water, your best bet is a cleaner containing ascorbic acid (vitamin C). Whereas if copper is the problem, citric acid is going to be the best active ingredient to deal with those pesky green stains. Once you know what metal you’re dealing with, you can purchase the best metal remover that targets the metal(s) that have invaded your pool.

Step #3 Follow the Manufacturer’s Guidelines: Each metal remover will have its own instructions and process to rid your pool of those nasty metal stains. Each cleaner contains a different combination of chemicals and will have specific rest, scrub, and filter times, depending on the metal stain you’re dealing with, so follow the instructions on the bottle for best results.

Removing Organic Pool Stains

Hello chlorine, my old friend. As we learned in our testing section, chlorine should always be your go-to cleanser for organic pool stains. Although you use chlorine regularly to sanitize the water, unfortunately, you’ll need a whole lot more cleaning power than your usual dose to take out rampant organic pool staining.

So, instead of spending your day scrubbing chlorine into every little stain, the easiest way to remove organic stains from around your pool is in one fell swoop. That’s right. We’re talking about pool shock. 

Pool shock is the strongest and most potent dose of chlorine you can add to your pool for the biggest sucker punch to those problematic stains. But we can’t just go tossing in chlorine shock willy-nilly. Let’s take it step by step.

Step #1 Test and Balance Your Pool Water: As a conscientious pool owner, you know that the number one rule about pool maintenance is to always test and balance the pool water before adding any chemicals or additives. 

We’re about to add a lot of chlorine here, so don’t worry too much about the chlorine levels. Instead, focus on the total alkalinity and the pH of the pool water. You probably already know this, but just as a refresher, we’re looking for alkalinity between 100-150 ppm (parts per million) and a pH between 7.4-7.6.

Balance and retest until you find the sweet spot.

Step #2 Shock the Pool: Once your pool water is properly balanced, the time has come to add the shock. A typical dose of chlorine shock is 1 pound for every 10,000 gallons of water in your pool. If your stains are minimal, this should do the trick. 

If you’ve been away for a while or a storm has taken a toll, the organic stains may have gotten out of hand. For a heavily-stained pool, you can double or even triple the dose of pool shock to get the job done. 

Pro Tip: For best results, always remember to shock the pool at night so as not to lose chlorine to UV radiation. 

Step #3 Brush, Brush, Brush: After adding the pool shock, grab your long-handled pool brush and give those stains a good scrub. Don’t worry if the stain doesn’t completely disappear with a bit of elbow grease, we still have a few more steps to go. 

Step #4 Run Your Pool Pump to Filter for 8 Hours: Now you can switch on your pool pump and take a break. Make sure that it runs for at least 8 hours to give the pool shock enough time to fully circulate throughout your pool.

Step #5 And Brush Some More: After the shock has had some time to make its rounds, try giving those stains another quick scrub with your pool brush to clear the last bit away.

Step #6 Recheck & Repeat: Recheck the stains after 8 hours. If they’ve disappeared, great! You’re all done. If you can still see some stubborn stains, start the process back at step one until they’re gone.

How to Stop Pool Stains Before They Start

Now that you’ve removed those unsightly pool stains, you want to make sure you prevent them from ever coming back.

To save you the hassle of removing future stains, let’s dive into the best practices for pool stain prevention.

How to Prevent Metal Pool Stains

  • Always use a hose filter when adding water to your pool, cleaning your filter, or any time you use the hose near your pool. Whether you live in a place with hard water or just aren’t sure about the quality of your local water, it’s a good idea to use a filter to keep things clean.
  • Frequently test your pool water for metals. There are home kits that do this, but as we mentioned earlier, it’s best to take a sample of your pool water into a professional to do the testing. That way, you’ll know for sure.
  • Frequently test your pool water, in general. Make sure to pay close attention to pH. If you pH fluctuates considerably, especially on the low side, the acidic pool water will start to corrode any metal plumbing you have in your pool. 
  • Use a Metal Sequestrant. If metal stains in your pool are a common problem, then it’s a good idea to start using a metal sequestrant as part of your regular pool maintenance. This chemical actually forces floating metal particles to cluster together, allowing your pool filter to clean them out automatically.

Pro Tip: Metal Stain Removers and Metal Sequestrants are NOT the same things. Sequestrants are a staple when it comes to preventing pool stains but once you have them, you’ll need a metal remover to get them out. 

How to Prevent Organic Pool Stains

  • Check your landscaping. Since organic matter is the cause of organic staining, it’s a smart idea to keep plants, shrubs, and trees located around your pool well-pruned to avoid getting leaves and fruit into your pool.
  • Frequently skim the pool surface to remove any organic matter that may have found its way in.
  • Keep the pool water balanced by testing weekly, paying special attention to pH, alkalinity, and sanitizer levels.
  • Vacuum your pool either manually or with an automatic pool vacuum to keep any debris from settling on the bottom and causing nasty stains. 

Stain-Free is the Way to Be

Now that you’re armed with the knowledge of how to identify, remove, and prevent pool stains, finding one in your pool doesn’t have to ruin your day.

Remember, regular and consistent pool maintenance is your best deterrent.

Categories: Pool Care, Pool Maintenance