Swimming Pool Stains Removal Guide

how to prevent and treat pool stains
Pool stains – yuck! Everyone wants their pool to be without stains. But sometimes those hard-to-remove spots and stains can take a bit more than just brushing. Here’s how you can treat and prevent unsightly swimming pool stains.

The first step to getting rid of those eyesore spots is to diagnose the stain type. Swimming pool stains can be caused by metals in the pool water, rust coming through the wall or by any organic material. The first clue to identifying the type of pool stain is the color of the stain.

A greenish-brown colored pool stain is generally due to something organic – such as leaves or mud sitting in the bottom of the pool over the winter. Algae, worms or other dead animals can also leave an ugly stain on your pool surfaces.

Pool stains that look reddish-brown, are very dark in color, or have a rust-like appearance to them are likely caused by metals. Copper stains in a pool will normally form blue, green, or black stains, while iron may cause rusty, brown, or green-brown splotches, and manganese will cause brownish-black or purple stains.

Berries or seeds can also create a red or blue stain. These are usually no surprise when they originate from plants surrounding the pool, but can be unique if brought in by birds or squirrels.

If this doesn’t help you determine the type, Jack’s Magic Stain ID Kit comes with sample packs of their pool stain removal products to try out on the stain before you purchase a a particular stain remover. Another option is to take a sample of your water to be tested for trace metals that may help identify the stain in your pool.

Organic Pool Stains

A super simple way to get rid of organic pool stains is to shock the pool and give your pool a little TLC with a good brushing. Generally this removes most organic stains in your pool. Pouring a small amount of chlorine shock right over an organic stain will usually make it disappear instantly. Works great on plaster pools, but don’t try this to remove stains on a vinyl pool, or you may also remove the liner pattern!

Localized stains can be removed with a device called the Jandy Stain Master and a gallon of muriatic acid. You can also pour acid into a piece of pvc pipe that you hold over a small spot on a plaster surface. Attach a 90 degree fitting on the end to deliver the acid to a stain on the pool wall. If the entire pool is lightly stained however, you may end up with a reverse stain – a bright white spot, surrounded by a darker color.

Stain EraserTo skip the harsh chemicals, consider the Stain Eraser. This product is made of a polymer with a built in mild abrasive to give your scrubbing an extra kick. It also comes with a tile grout scrubber to get in between those fine cracks. There are two different types of heads – one for a concrete pool and the other for a vinyl pool. Attaches to your pool pole to remove those hard to reach pool stains.

If your stain is all around the waterline of the pool because of material floating at the Pool First Aidtop, use an enzyme-based cleaner such as Natural Chemistry’s Pool First Aid. Enzyme-based cleaners help to break down organic compounds and oils by speeding up the chemical reactions that assist in making stains virtually disappear on their own. Follow up with a good brushing again to make sure you’ve got all the left behind debris and oil.

Organic pool stains are not so hard to remove, but over time, it will give your pool a dull light-brown appearance. It’s hard to notice because it happens so slowly. Eventually you may decide to drain and acid wash a plaster pool. This is not something that you can do often, as it involves a purposeful stripping of a thin layer of pool plaster. For some pool owners who want to restore the bright white surface – an acid washing can be a good solution, every five years or so.

Metallic Pool Stains

If you have determined that you have a metallic stain, the first thing to do is to reduce and remove the trace metals in your pool water. One such very effective product would be Natural Chemistry’s Metal Free. This product is especially great at removing iron and copper from your pool, which can be a major issue, especially if you fill your pool with well water. If you just treat the stain and neglect to take care of the imbalance of metals, the stain will just keep returning.

stain-free-bwA powerful follow up to target stains left by metals is Natural Chemistry’s Stain Free. Stain free is an ascorbic acid based pool stain remover. That’s right – Vitamin C, and it makes a great pool stain remover. Linus Pauling would be so proud!

One way to test if Stain Free would work on your particular pool stain is to grind up a small handful of Vitamin C tablets from your medicine cabinet, and sprinkle these over the stained area. You may be surprised at how well Ascorbic Acid works to remove pool stains!

Any of these products should make current stains disappear and old stains lighten right up if you treat the metals in your pool correctly. If the staining has reached your pool steps and they need an extra scrub, try Jack’s Magic Step Stuff to whiten your pool steps back to brand new condition.

Preventing Pool Stains

To keep organic pool stains out of your pool, do your best to keep the pool clean. This may involve trimming trees or bushes around the pool, investing in a better winter pool cover or an automatic pool cleaner.

Some of the worst pool staining can occur from mudslides or mulch-slides into the pool. For those that find it impossible to correct these conditions, recoating the pool with a dark colored plaster or liner will help to hide the resultant pool stains.

To prevent metallic stains from returning, make sure to regularly test your water for metals, as the stains will keep coming back if you have a highly metallic pool. Metals in your water can come from well-water, or from iron or copper pipes.

A common cause of blue-green copper pool stains is improper chemical maintenance. Low pH and high chlorine levels can also erode the copper heat exchanger in a pool heater. Maintaining proper water balance makes it easier to keep pool stains from occurring in the first place.

Metals are not uncommon in pool water, and they can be hard to remove from the water. Instead of removing the metals, sequester them with a Stain & Scale product. Sequestering agents, also known as Chelators, tie-up minerals in solution – it’s when they come out of solution, floating free in the water, that they can deposit themselves as stains on your pool surface. Two sequestering agents that are especially useful are Super Stain Away or Jack’s Magic Blue Stuff.culator-packet

Metals are not impossible to remove from pool water. If you have severe metallic pool stains in your pool, try CuLator Metal Eliminator. Drop the disposable absorbent bag into your skimmer basket and it absorbs metals such as Copper, Iron, Manganese, Cobalt, Silver, Nickel.

Hopefully these suggestions will help you understand pool stains a bit more and provide some useful methods for effective pool stain removal. A great way to avoid stains before they start is to make sure that you keep your pool clean, your chemical levels balanced, and your minerals sequestered.

Where pool stains are concerned, an ounce of prevention is worth a pound of cure, and in this case, a hassle free beautiful pool!



Sabrina Potirala
InTheSwim Staff Blogger


Swimming Pool Stains Removal Guide — 7 Comments

  1. Hi, I would like to ask if you have come across black spots on the surface of the pool lining. The lining is Quartzon and only 4 months old and the pool is mineral. The black spots don’t have a head as I have tried to scratch them off. The water balance is normal and I have kept the water slightly acidic in hope the spots will go away. Thoughts?

    • Hi Tim, black stains that are not calcium crystals or black algae, could be mineral staining. If your pool uses a power ionizer, staining can result from overuse – copper and/or silver staining. Cobalt or manganese in the fill water can also produce dark spots, or it could be rust, from accidental metal shavings or pieces getting into the pool. It could also be stains from berries or tree nuts or animal waste – these will remove easily with chlorine shock sprinkled over the stain. If that doesn’t work, you can try sprinkling Stain Free or use a stronger acid like Stain Away over the spots. If that doesn’t work, draining and acid washing the Quartzon (a type of pool plaster, for those that don’t know) to remove the stains.

    • Hi, must be frustrating. Black spots you say? Could be Black Algae, lets just throw that one out there right away. If you inspect it closely (underwater with a mask), you will be able to tell if it’s algae, even if it won’t brush off easily, it will scrape off. Now it could also be metal staining, minerals such as manganese, or copper can make streaky black stains, maybe dots and spots, too. Thirdly, you could have stains from berries or acorns, or something – these would lift immediately with granular chlorine sprinkled over top, and a light brush. If shock doesn’t do anything, you can try crushed up Vitamin C tablets, and if that works, you could use Stain Free Ascorbic Acid stain remover. If neither of those works, you could use one of our Stain Away chemicals. But first, make sure that it’s not algae, and be sure the water balance is perfect, and that you are filtering and sanitizing and cleaning properly. Hope that helps, Good Luck!

    • Hi Ryan, using enzymes regularly can help control oily deposits and prevent waterline staining. Most waterline deposits are a mixture of dust, calcium, oils, etc. When calcium is very high in hard water, a white-ish scale can form at the waterline. Black or Grey-ish, you say? Try to see where it is coming from, (mulch, pollen, dust, auto/plane exhaust, oils, grease, soil).

      If you have TILE, you can lower the water level a bit, and scrub it clean with small amounts of abrasive cleanser, like Comet or Bon Ami. Use a textured sponge and apply pressure. This is easiest done inside the pool, in most cases. If there is scale deposited on the tile, you can add a cup of muriatic acid to a spray bottle that already has 2 cups of water inside. Wear goggles and gloves and spray over wet calcium scale, then scrub it with a brush, or scrape it with a putty knife, then splash off the acid with pool water. You can adjust the strength of the acid as needed.

      If you have VINYL, you can lower the water, but you don’t want to use anything as strong as acid or chlorine. Natural Chemistry makes a good enzyme based pool cleaner called Clean & Perfect, or use a pool tile and vinyl cleaner like, we have two – regular and ‘super’, which is more concentrated. These are mild enough to not harm vinyl liners, but strong enough to remove most waterline deposits.

  2. Pingback: Pool Stains and Discoloration in a Marcite Pool | InTheSwim Pool Blog

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