How to Identify and Remove Pool Stains

If you’re a pool owner, having a clean and welcoming swimming space is a top priority, but even if you put plenty of time and effort into pool maintenance, unsightly stains can develop.

Unfortunately, pool stains often withstand routine cleanings and can be more challenging to tackle than simple dirt or debris. If you’ve spotted a nasty stain in your pool, you don’t have to worry! We’ve put together a list of straightforward steps you can take to get your pool looking good as new.

What Causes Pool Stains?

The first step to removing a pool stain is identifying what caused it in the first place, which can be determined 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 two categories.

Organic Pool Stains

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

Metal Pool Stains

Metal pool stains are caused by the introduction of metal—usually copper or iron— to your pool. According to the Independent Pool and Spa Service Association (IPSSA), Copper stains are prevalent and are often caused by algaecides, fill water, 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.

Pool Stain Colors

One of the most effective ways to identify whether you have an organic or metal pool stain on your hands is to observe the stain’s color. Some colors indicate an organic stain, while other colors mean a metal stain that might be a little more tricky to get rid of.

  • Blue-Green Stains 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.
  • Purple Stains and precipitate on pool tile lines and the surface of a pool appear with an excess of copper cyanurate and are evidence of a metal pool stain.
  • Brown Stains signify iron dissolution and are often indicative of iron buildup.
  • Green-Brown Stains are caused by leaves, dirt, and other debris surrounding the pool area and signify organic stains.
  • Red-Blue Stains are evidence of berry residue and are likely to appear in the event that a berry-producing plant resides near the pool.

Testing Stains

While the color of a stain can often help you identify whether a stain is metal or organic, there are circumstances where it is more difficult to discern. The last thing any pool owner wants to do is end up misdiagnosing a stain, and using the wrong materials to get rid of it.

Sometimes, pool owners will enter a pool store complaining of a green stain and are advised to treat the stain with algaecide (which, as we noted, can actually be the source of a green copper stain).

Mistaking metal marks for organic ones is an easy problem to avoid if you follow these simple tests to discern the nature of the stain you are dealing with.

Testing Organic Stains

If you suspect you have an organic stain on your hands, 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.

Testing Metal Stains

If you’ve already ruled out an organic staining issue, it’s likely you’re dealing with a metal stain. Since chlorine has no effect on metal, you’ll have to take a different approach. In the case of a metal stain, apply a small amount of citric or ascorbic acid—in the form of a dry powder or granules— to the affected area.

How to Get Rid of Pool Stains

Once you’ve learned about the organic and metal stains, determined which colors they present, and deciphered which type of stain is tainting your pool, you’ll want to put a plan in place for removing the blotches altogether.

Removing Organic Stains

Adding chlorine is not only the best way to test whether you have an organic stain on your hands but also the most effective method for removing organic stains from your pool in their entirety.

According to the American Chemistry Council, when added to water, chlorine disinfectants eliminate water-borne germs found in organic materials that stain a pool, such as algae. Often, the presence of organic stains indicates 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 is a process of adding oxidizing chemicals to pool water and boosting chlorine levels to destroy bacteria.

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

  • Test the pool water. Be sure to test the total chlorine, the FAC level, the pH level, the pool’s alkalinity, and 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.
  • Leave your pump and filter running. Shock treatment works best when allowed to circulate, preferably for up to eight hours.
  • Treat your pool after the sun sets. Shocking your pool is most effective after dusk, as it prevents the chlorine from losing effectiveness, which can occur with ultraviolet ray exposure during the day.

Removing Metal Stains

Eliminating metal stains can be slightly more complicated and time-consuming than tackling organic stains, but the process is straightforward. We recommend treating copper or iron stains with a combination of citric or ascorbic acid stain remover 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 make sure it is balanced properly is an important first step. Additionally, it is possible to determine exactly 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. Ensure you apply a treatment that specifically targets the metal you tested the pool water for, as treatments can 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 that would require further action to be removed. If opting for a non-phosphate sequestering agent, consider that these products typically only work on new stains that haven’t yet reached the pool’s surface.

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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. There are measures you can take to fend off both organic and metal pool stains.

Preventing 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 the pH, FAC, total chlorine, and alkaline levels in your pool water 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 an excessive amount of leaves, debris, or berries, consider moving them or trimming branches wherever possible.

Preventing Metal Pool Stains

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

  • Keep your pool water balanced. This is a key component in general pool maintenance and an effective way to prevent both organic pool stains and metal pool stains. Most staining is a direct result of imbalances.
  • Test your pool water for metals. Using the 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. If you use well water to fill your pool, utilize lawn care services that frequently apply fertilizers to your lawn, or have worn out pool plumbing, be sure to check your metal levels more regularly.
  • Adopt a sequestering agent in your weekly, biweekly, or monthly pool maintenance routine. This will keep metals from gathering into splotchy stains on pool surfaces.

Say Goodbye to Stains!

Pool stains, while displeasing to the eye, are not unbeatable. Once you conquer algae, iron, or copper buildup, you’ll be free to swim to your heart’s content.

If you follow the necessary steps to remove organic stains or metal-based stains using pool shock or a combination of citric or ascorbic acid and a sequestering agent, you’ll be on your way to a stain-free pool.

Prevention is half the battle when it comes to pool stains, so 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. Who knows? You might even have the cleanest pool in the neighborhood.

Have questions? Feel free to shoot us a message.

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