How to Identify and Remove Pool Stains

Pool stains can become an unnecessary headache for pool owners and, if left unattended, can cause damages that rack up your monthly maintenance costs.

To address this problem, first identify the source of the stain, and implement the appropriate solution as soon as possible. Using tools like the pHin smart monitor can help you quickly identify significant issues with your water chemistry caused by pools stains.

These stains generally fall into two categories – metal or organic – and the best way to distinguish them is by color. Whether it’s a green-brown or brown-black-purple mix, different color combinations can highlight the exact substance causing the stain. This article will cover how to approach those stains and prevent future staining to achieve a healthier pool.

Dealing With Organic Pool Stains

Organic stains are caused by leaves, berries, and other organic debris that settle on pool surfaces or even sink down and decay on  your pool’s floor. These stains are typically green, brown, or bluish-purple. The best way to address these stains are by super chlorinating the water, followed by a thorough brushing. First test the water using products like the pHin smart monitor to check the balances of pH and alkalinity. Ideally pH should be between 7.4 and 7.6, while alkalinity should be between 100 and 150 ppm (parts per million).

Once tested, proceed to shock the stain directly with chlorine to remove it. For multiple or large stains, triple shock your water by adding 3 pounds of pool shock for every 10,000 gallons of water. For the best results, shock your pool are at dusk or at night. After your pool is properly shocked, thoroughly brush the stained area, and let the pool circulate for at least eight hours. While keeping the chlorine levels high, brush the stains intermittently until the stains are finally gone.

Handling Metal Pool Stains

Metal stains are commonly caused iron, manganese and copper, and can be a little more difficult to get rid of, but not entirely impossible. Here’s are some of typical locations where you’ll find these elements.

  • Copper originates from and the corrosion of copper and brass pipes. This causes a blue, green, teal, black or dark purple stain.
  • Iron comes from water corrosion of iron pipes and fittings, and results in rusty brown, gray or greenish-brown stains.
  • Manganese is from well water and results in pink, dark brownish-black or purple stains
  • Calcium may also cause stains that appear as white crystals, and typically they come from plaster, mortar or cal-hypo chlorine shock.

Before taking any action to treat for stains, check what caused the stain, as green, yellow, or black stains may actually be a result of algae, not metal. Take some citric acid from a lemon/lime/orange or vitamin C tablet and apply directly to the stain, and it will chemically lift any copper or iron stains in your pool.  

After you’ve confirmed the presence of metals, make sure that you water is balanced and your chlorine level is 1.5ppm or less (use the pHin smart monitor for accurate measurements). Once balanced, apply ascorbic acid to remove the stains from the affected areas and the stains should be chemically lifted within a few minutes of the application.  Following this step, add a sequestering agent, to bind up the minerals and help move them into your filter system so they can be removed once your clean your filter system. It is recommended to use the sequestering agent on a weekly basis to keep deposits from re-forming. Be sure to regularly check your filter for the sequestered metals, and do not shock your pool a few days prior and after a metal treatment.  

Aside from physically cleaning or vacuuming your pool service, pool stain treatment is an important part of pool maintenance. Keeping an eye out for organic or metal stains require that you make sure pH and alkalinity are balanced  to keep your sanitizers and sequestering agents to work properly. If you want to ensure you, your pool or your hot tub continues to stay healthy, keep it balanced with pHin. It constantly monitors your water and tells your smartphone what you need to do to keep the water in your pool and your hot tub healthy. Use it with your own chemicals for flexibility or get our single-dose, pre-measured chemicals delivered to your door. If you need someone to service your equipment, Pool Service on Demand connects you to local, qualified pool techs.

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