How to Remove Pool Stains of Every Type (& Prevent Them From Coming Back)

Written by Michael Dean
January 6, 2024

removing a pool stain

Maintaining a clean and sparkling pool is a top priority for every pool owner. But even if you put plenty of time and effort into basic swimming pool maintenance, pool stains can develop on the walls and floor.

Unfortunately, pool stains are hard to get rid of. You will need to go further than a routine cleaning to tackle them. I’ve put together a list of straightforward steps to get your pool looking as good as new when you tackle stains.

Main Takeaways

  • Pool stains are caused by algae, leaves, excess metal, rusty objects, excess calcium, and buildup of dirt and debris.
  • To differentiate organic and metal stains, use concentrated chlorine on a suspected organic stain and vitamin C on a suspected metal stain.
  • The methods to clear pool stains differ depending on the type of stain you are dealing with.
  • To prevent pool stains from returning, you must maintain chemical levels (especially pH) and have a regular cleaning and maintenance schedule.

What Causes Pool Stains?

The first step to removing a pool stain is identifying what caused it in the first place. You can determine the type of stain by observing its color and performing an identification test.

Types of Pool Stains

If you spot a stain in your pool, it will fall into one of five categories.

Organic Pool Stains

Organic pool stains are caused by natural materials from the environment surrounding your pool, such as algae, berries, leaves, and other debris.

Metal Pool Stains

Metal objects, such as copper and iron, can cause stains in the pool when introduced to the water. According to the Independent Pool and Spa Service Association (IPSSA), copper stains are prevalent and are often caused by algaecides or worn pool plumbing.

Iron stains are caused by the erosion of improperly installed pool heater headers, lawn fertilizers, and, most commonly, the use of well water. You can read my article on how to get iron out of pool water for strategies you can use to remove it. I also have an entire article on removing metal stains from your pool.

Rust Pool Stains

Rust pool stains come from rusting metal objects sitting in the pool. While pool equipment, like ladders, can certainly rust, these types of stains can also occur from other metal objects in the water, such as hair pins and nails.

Calcium Buildup Pool Stains

Excess calcium can leave deposits and build-up on your pool surfaces that can be unsightly and uncomfortable for swimmers.

Waterline Pool Stains

Waterline stains are often the result of dirt and debris entering your pool water, such as leaves, dirty feet, sunscreen, and more. These stains occur, you guessed it, on the waterline of your pool.

Pool Stain Colors

Observing the color of the stain is one of the best ways to determine what type of stain you are dealing with.

Blue-Green Stains

Blue-green stains usually indicate copper stains, but if the surrounding pool water is cloudy and the stain is slimy in texture, a greenish color could also indicate an algae-induced organic stain.

blue green pool stain

Purple Stains

Purple stains on pool tile lines and the surface of a pool appear due to an excess of copper cyanurate and are evidence of a metal pool stain.

purple pool stain

Red-Brown Stains

Red-brown stains signify iron dissolution and are often indicative of iron buildup.

red brown pool stain

Green-Brown Stains

Green-brown stains are caused by leaves, dirt, and other debris surrounding the pool area and signify organic stains.

green brown pool stain

Red-Blue Stains

Red-blue stains are evidence of berry residue and are likely to appear if a berry-producing plant resides near the pool.

red blue pool stain

Brown Spotted Stains

Brown spotted stains are normally caused by rust in the water and are evidence of rusty metal sitting in the water.

brown spotted pool stain

White-Gray Stains

White-gray stains occur due to excess calcium in the water. This is evidence of calcium build-up.

white grey pool stain

Yellow-Brown Waterline Stains

Yellow-brown waterline stains point to a build-up of unwanted dirt and debris in the water.

yellow brown waterline pool stain

Yellow-Green Stains

Yellow-green stains are a sign of mustard algae, especially if the stain is slimy to the touch. I cover how to clear up and prevent mustard algae in depth in a separate post.

yellow green pool stain

Black-Purple-Brown Stains

Black-purple-brown stains are a sign of manganese staining. This can be an issue for pools that are filled with well water.

black purple brown pool stain

Black-Green Spotted Stains

Black-green spotted stains may indicate a black algae infestation. Check out my article on removing black algae for information on clearing this up.

black green spotted pool stain

Pink Film-Like Stains

Pink film-like stains most likely occur from pink slime, a pink bacteria that looks and feels similar to algae (but pink). Check out my article on getting rid of pink slime in your pool if you have pink stains.

pink film like pool stain

Grey-Black Stains

Grey-black stains can occur do the overuse of algaecides with silver in them. Silver stains are uncommon but are fairly difficult to remove.

grey black pool stain

How to Test For Organic And Metal Stains

While the color of a stain can often help you identify what kind of stain it is, there are circumstances where it is more difficult to discern. Misdiagnosing a pool stain and treating it with the wrong materials is the last thing you want to do as a pool owner.

It is common for pool stores to immediately recommend algaecide for green pool stains. However, if the pool stain turns out to be from copper, algaecide can actually make the stain worse.

Waterline and calcium buildup stains are a lot easier to discern. Waterline stains affect, as the name suggests, the waterline only. And calcium buildup stains are white or gray in color, making them a lot easier to differentiate from other stains. On the other hand, organic, metal, and rust stains can be difficult to distinguish from one another. Follow these simple tests to discern the nature of the stain you are dealing with.

How to Test For Organic Stains

If you suspect you have an organic stain in your swimming pool, the best course of action is to apply a small, concentrated amount of chlorine to the area in question. This will eliminate an organic stain. If the stain does not disappear, you are likely dealing with a metal stain.

How to Test For Metal Stains

Since chlorine does not affect metal, you’ll have to take a different approach with metal stains. Apply a small amount of citric or ascorbic acid (vitamin C tablets) in the form of a dry powder or granules to the affected area. If this removes or at least lightens the stain, it is a metal stain.

How to Test For Rust Stains

While rust stains can also be affected by vitamin C tablets, to determine whether you are dealing with rust or metal, rub the affected area with dry acid or sodium bisulfate. If it’s rust, the problem area should start to fade away.

How to Quickly Get Rid of Pool Stains

Now that you know how to identify and test for the type of stain, you’ll need to go through the steps for removing the stain. The methods for removing stains differ according to the type of stain you are dealing with.

How to Remove Organic Stains

Adding chlorine is the best way to test whether you have an organic stain and the most effective method for removing organic stains from your pool.

According to the American Chemistry Council, when added to water, chlorine disinfectants eliminate water-borne germs found in organic matter that stain a pool, such as algae. Organic stains often indicate that the “free available chlorine” or FAC level in your pool is too low.

The best way to treat an organic stained pool with chlorine is to raise the FAC levels by “shocking” the pool, which adds oxidizing chemicals to pool water and boosts chlorine levels to destroy bacteria.

Here’s an outline of the steps you can take to get rid of organic stains that discolor your pool walls:

  • Test the pool water. Test the total chlorine, the FAC level, the pH level, the pool’s alkalinity, and the calcium hardness of your pool. The Association of Pool and Spa Professionals recommends maintaining a FAC of 2.0-4.0 parts per million (ppm), a pH level of 7.2-7.8 (ideally 7.4-7.6), total alkalinity of 100 ppm, and calcium hardness of 200-400 ppm.
  • Shock the pool. Following the instructions provided on your pool shock product, super chlorinate your pool by adding ten times the total chlorine. You can achieve this by adding a higher dose than the standard pool shock treatment, which is roughly 3 pounds of calcium hypochlorite shock per 10,000 gallons of water in your pool.
  • Brush your pool. Vigorously brush the sides of the pool, wherever the stains are located. You may not be able to remove all of the stains at this time, but it will help with the process of breaking up the organic material.
  • Leave your pump and filter running. Shock treatment works best when allowed to circulate, preferably for at least eight hours.
  • Give the pool another scrub. After the pool has circulated for a while, give it another scrub. This should help remove any remaining stains on the sides of the pool.
  • Treat your pool after sunset. Shocking your pool is most effective after dusk. It prevents chlorine from losing effectiveness, which can occur with ultraviolet ray exposure during the day.

Organic stains can usually be removed using chlorine shock, brushing, and standard pool cleaning protocol. If the organic stain is extra stubborn, I recommend applying chlorine directly to your pool brush and scrubbing. With some elbow grease and willpower, you can remove the staining. If you have extensive algae staining that will not scrub off, it may be time to acid-wash your pool surfaces. I cover this in my acid washing guide.

How to Remove Metal Stains

Eliminating metal stains is slightly more complicated and time-consuming than tackling organic stains, but the process is still straightforward. I recommend treating copper or iron stains with a combination of citric or ascorbic acid and a sequestering agent.

Follow these steps to treat your pool for metal stains:

  • Test the water to determine the source of the metal. As with removing organic stains, testing your water to ensure it is adequately balanced is an essential first step. Additionally, it is possible to determine which metal is causing a stain with a home test kit.
  • Apply citric or ascorbic acid granules. Using either a liquid or dry acid treatment, apply the stain remover to the pool and allow it to filter. Apply a treatment specifically targeting the type of metal you tested the pool water for, as treatments vary.
  • Add a sequestering agent. This will help your pool’s filtration system filter out the metals the acid granules lifted. Note that some sequestering agents contain phosphates (food for algae) that require further action to be removed. If you choose a non-phosphate sequestering agent, it is worth noting that these products typically only work on new stains that haven’t yet reached the pool’s surface.

Best Metal Stain Remover

Metal stains can be removed with ascorbic acid (vitamin C) or citric acid and Metal sequestering agents. Natural Chemistry’s Stain Free Extra Strength stain remover is a great option to really go to town on stubborn metal stains.

Natural Chemistry Extra Strength Stain Free
View on Amazon
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Pool Mate’s Metal Out is an excellent sequestering agent that prevents metallic stains in your pool. Both of these options will also help with rust stains.

Pool Mate Metal Out
View on Amazon
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

How to Remove Rust Stains

While there are a few different methods to remove rust stains, including using a standard stain remover or even muriatic acid, my preferred method to remove rust stains is to use vitamin C, which is a lot gentler than using muriatic acid (you can also use muriatic acid to clean pool tile). As rust stains are essentially a type of metal stain at the end of the day, you can use a vitamin C tablet to remove it from your pool surface. Follow these steps to successfully remove these unsightly rust stains from your pool surface.

  • Add vitamin C tablets to a clean sock. Yes, a sock! Add around 10 to 20 vitamin C tablets.
  • Put the sock on the stain. Simply place to sock on the problem area for about a minute or so, and then rub on it.
  • Brush away the stain. Use a pool brush to brush the rust stain away.
  • Repeat, if necessary. If the stain is still there, put the sock on the stain for another minute, rub on it, and then brush the area once again.

How to Remove Calcium Buildup Stains

To remove calcium scale deposits on your pool, you’ll need to first determine whether you are dealing with calcium carbonate or calcium silicate. To determine the type of calcium deposit scale you are dealing with, mix a few drops of muriatic acid with a bucket of your pool water and check to see if it reacts. If it reacts and foams, you are dealing with calcium carbonate. If it doesn’t react, you are dealing with calcium silicate.

To remove the scale, follow the below steps:

  • Test the water. Before you do anything, test the water. Test for what type of calcium scale you are dealing with and check to make sure the other pool chemical levels are in the correct range. If not, adjust them.
  • Lower the calcium hardness. To remove calcium stains, you need to lower the calcium hardness level of your water. Aim for 200 – 400 ppm.
  • Adjust the alkalinity. Once the calcium hardness level is sorted, get your pool’s alkalinity under control. The ideal levels are 80 – 120 ppm.
  • Check the pH. You should also check the pH of your water and ensure it’s between 7.2 and 7.6.
  • Clean and scrub. Now that your pool chemistry is in order, use a combination of scale eraser, scale remover, and scrubbing to remove the white-gray stain from the pool surface.

When dealing with calcium carbonate, in particular, you should use a pumice stone to remove the stain from the walls. When using a pumice stone, ensure the surfaces are always wet. Alternatively, you can use a stain eraser or a calcium scaling treatment.

For more information on how to remove calcium stains, check out my complete guide on removing calcium scale deposits from your pool wall.

Best Calcium Stain Remover

If you have tried scrubbing calcium scales with a pumice stone or scale eraser, you might need a bit of help from a calcium releaser. I recommend LayorCare’s Heavy Calcium Remover, which is an acid-free remover that doesn’t damage your pool’s surfaces but allows you to remove calcium deposits with minimal elbow grease.

LayorCare Heavy Calcium Releaser
View on Amazon
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

How to Remove Waterline Stains

Thankfully, removing waterline stains is not as difficult as other stains. Generally, waterline stains are caused by debris, so the first step is removing the dirt and debris from the pool. To do this, skim the surface of the pool with a net, vacuum the pool, and empty any skimmer baskets. You should also clean out your filter system to ensure that everything is squeaky clean. Once you’ve done that, follow these next steps:

  • Brush the waterline. Use a stiff brush and circular movements and work on the stains on the waterline of your pool. If the buildup is really minimal, you can even use a cloth or a smaller brush, like a toothbrush.
  • Use a cleaner. Along with the brushing, apply a cleaner on the problem areas. For minimal buildup, you can use a household cleaner, like vinegar, baking soda, or dish soap. But for more stubborn stains, try a stain eraser product that you can buy at your local pool store.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

Something went wrong. Please check your entries and try again.

How to Prevent Pool Stains from Returning

One of the easiest ways to combat pool stains is to take the necessary precautions to prevent them before they occur. You can take some measures to fend off all types of pool stains.

How to Prevent Organic Pool Stains

Preventing organic pool stains is a matter of regular cleaning and maintenance. The following are best practices for keeping environmental factors from contributing to stain development:

  • Keep your pool water balanced. The most effective way to prevent organic pool stains is to regularly monitor your pool water’s pH, FAC, total chlorine, and alkaline levels and adjust your treatment based on the Association of Pool and Spa Professionals’ guidelines.
  • Keep your pool clean. There are many ways you can monitor and maintain your pool’s cleanliness. Some of the best methods are to invest in an automatic pool cleaner or vacuum your pool by hand, brush your pool walls, and regularly skim your pool’s surface to prevent any debris or dirt accumulation.
  • Clear your pool of unnecessary surroundings. If your pool is surrounded by plants that shed excessive leaves, debris, or berries, consider moving them or trimming branches wherever possible.

How to Prevent Metal Pool Stains

While preventing metal pool stains requires more attention and a few additional provisions than preventing organic stains, following these guidelines will help keep metals from developing marks on your pool’s floors, walls, and surfaces.

  • Keep your pool water balanced. This is crucial in general pool maintenance and the primary method to prevent organic and metal pool stains. Most staining is a direct result of chemical imbalances.
  • Test your pool water for metals. Using at-home test kits to ensure that you don’t have an excess level of metals in your pool water is an effective way to prevent staining.
  • Be aware of factors contributing to increased metal levels in your pool water. Regularly check the metallic levels in your water if you use well water to fill your pool, if you frequently apply fertilizers to your lawn, or if the plumbing of your pool system is old and worn.
  • Adopt a sequestering agent in your weekly, biweekly, or monthly pool maintenance routine. This will keep metals from gathering into splotchy stains on the pool’s surfaces.

How to Prevent Rust Stains

Although rust stains are technically a type of metal stain, preventing rust stains is a whole other animal, as other elements cause these types of stains. The following steps should help you avoid getting these stains on your pool in the future:

  • Clean or replace any rusty equipment. If your pool ladder or other pool equipment is rusty, remove them from your pool and clean them. If you are unable to clean the equipment, replace them entirely! Even if you clean the rust stain, it’ll only return if you do not get rid of the cause.
  • Remove any metal objects in the water. You should be regularly skimming and cleaning your pool. If you notice any foreign metal objects in the water, remove them immediately. Even if the metal object is not already rusty, the chemicals in your pool water will cause the metal to rust eventually, causing rust stains.

How to Prevent Calcium Buildup Stains

The best way to deal with calcium stains is to prevent them from building up in the first place. Here are some of my top tips for preventing these white-gray stains from clouding up your pool water:

  • Apply a calcium blocker to your pool surfaces. This product will not only protect your walls from calcium buildup but will also help the longevity of your pool.
  • Regularly test your pool water, and ensure the calcium hardness level doesn’t go beyond recommended levels.
  • Maintain your pH balance, and ensure it is always within ideal levels. Preventing the pH levels from going too high or low will help deter the calcium levels from going awry.
  • Install a pool cover to prevent evaporation. Evaporation of the pool water makes the chemicals in your water, including calcium, become more concentrated.

How to Prevent Waterline Stains

Preventing waterline stains means keeping your pool clean and maintaining a good pool maintenance schedule. To ensure you never get waterline pool stains again, follow the below advice:

  • Regularly clean your pool. This point cannot be stressed enough. Regular cleaning should be a normal part of your pool maintenance routine. Brush, vacuum, and skim the pool regularly and whenever you notice your pool getting particularly dirty.
  • Brush your waterline at the start of every pool season to give it a thorough preventative cleaning. To do this, make sure to lower the water levels slightly.
  • Maintaining chemical levels is some of the best advice I can give you to prevent many different types of stains – including waterline stains.

Say Goodbye to Stains!

While displeasing to the eye, swimming pool stains are nothing to panic about. Once you conquer the buildup, you’ll be free to swim to your heart’s content. And with my research, you can remove various stains efficiently. I also wrote another article on removing stains from vinyl pool liners if you’d like to read that as well.

As long as you check your pool’s pH levels frequently, adopt a regular maintenance routine, and invest in preventative pool treatment, you’ll be rid of stains for good!

Have questions? Feel free to shoot me a message.

Scroll to Top