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How To Identify Pool Stains

How To Identify Pool Stains
By Pools Above Ground
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How To Identify Pool Stains

This article may pertain more to concrete pools than above ground pools for the simple reason that you can do things to the concrete pools' surface to remedy the issue that you could not do on vinyl. Here are a couple of examples of what I mean. You may be able to use a wire brush on concrete surface or scrub the stain with a chlorine tablet. This is something the a vinyl liner just can't take without damaging it. 

Still I decided to put this article up because it shows you the causes of pool stains and highlights the importance of keeping your pool clean and water chemistry in check. Vinyl pools liner for above ground pools or inground pools are certainly cheaper to replace than re-surfacing a concrete pool but when they're stained you probably will not be able to remove it. On the other hand, some of the problems listed below don't really occur in vinyl pools because the material isn't porous like concrete and they just can't take root in the vinyl's smooth surface.

Swimming Pool Maintenance

Maintaining the health of your pool is a full-time job. Luckily, we have chlorine, stabilizer, and other chemicals to do most of the work for us. However, when the water becomes improperly balanced due to too little (or too much) of any one element, problems can start to creep up pretty quickly. One of the signs that your pH, alkalinity, or sanitizer levels are out of whack is that stains will start to form on your pool lining. If you don't act quickly, these stains are just the first step in a complete takeover of your pool. In this article, we'll talk about how to identify some common pool stains, their causes, and - most importantly - what to do about them.


Frequent Causes of Pool

When stains start to show up in your pool, it isn't always indicative of a problem with your chemical levels. Sometimes, the decay of organic matter (a chemical process in its own right) is enough to leave stains in an otherwise healthy pool. Examples include debris like leaves, berries, and acorns, which will leave a distinct brown discoloration as they start to break down. Next, you have algae. These are tiny water-based plant organisms similar to seaweed. Not only do they multiply like crazy in the proper environment, but they can turn your pool into a slimy, grimy mess in a matter of days. Three types of algae commonly show up in pools: green, black, and yellow. Each one will pose its own problems and require its own solutions. You might not think of it, but your pool water contains an abundance of metals like iron and copper. If these levels become elevated, they can start creating stains on the surface of the pool. This is a slow process, as it requires the water to evaporate while the metals build. However, if you don't pay close attention, the stains will simply seem to "appear" one day.

Properly Identifying Pool Stains

It’s not always easy to identify different pool stains. Usually, you'll have to head to Google or to a pool forum to figure out just what's causing your pool problems. However, this is little more than a guessing game. And since different stains have different solutions, the game could turn out to be incredibly expensive. So, to help you make the right decision for your pool, we'll describe some of the most common pool stains (and their sources) in detail below. Organic Stains – Noticing a brown, dusty type stain on the bottom of your pool? This is likely due to organic material like leaves and acorns falling into the pool. If you don't skim them out in time, they will start to break down and leave acidic tannins lingering behind. In fact, it's not at all uncommon to see brown stains in the perfect shape of a leaf on your pool floor. Iron Stains – Iron stains tend to appear near pool components like drains, filters, etc. This is because iron needs a surface upon which to build up, and the molecules won't bind as easily if they're free-floating in the pool. You can identify iron stains as yellow or dark brown rust that looks gritty to the touch.

Copper Stains – Copper stains are a bit more difficult to identify, but they typically show up as "zebra stripes" on the side of the pool. Depending on your water's chemical makeup at the time, these streaks will be gray, black, or bluish in color.

Manganese Stains –  Manganese is most often found in well water, so it's not common everywhere in the US. However, it is extremely easy to identify due to the purplish hue it gives the pool.

Green Algae Stains – As the name implies, green algae will turn both your pool liner and the water itself a disgusting green. As green algae are great at reproducing, what starts as small areas of buildup can quickly move on to affect the entire pool.

Yellow Algae Stains – Yellow algae is a bit easier to identify, as it tends to look as if someone were stomping on mustard packets near the walls of your pool. Though all of the water might not change color, you’ll still need to act fast to get rid of this invasive species.

Black Algae Stains – Rather than streaking or striping, black algae appears as small black specks dotting the lining of your pool. Aside from looking gross, black algae also grow roots into your pool surface. This can often make it even harder to get rid of.

How to Test for Pool Stains

When it comes to identifying iron stains, you can actually skip the trip to the pool store and instead hold a Vitamin C tabled against the area. If the stain gets lighter or disappears, you know you're dealing with an iron infestation. Once you're sure, you can use ascorbic acid to remove the iron altogether. Most tannin stains from leaves and other organic debris are easy to recognize due to their color and shape. However, they will also lighten in color if you press a trichlor tablet against the surface. Once you're sure that you're dealing with organic remnants, you can take steps to raise the pool's free chlorine levels and remove them. For other stain types, you’ll need to get your hands on a Stain ID kit from your local pool store. This will allow you to perform some simple steps to determine what kind of algae or metal is affecting your pool water. Such a stain ID kit will also recommend the proper procedure for getting rid of the stain (and its cause). This will ensure you don't waste your hard-earned money treating copper with an algae solution – or vice versa.

If you have further questions or need a new pool liner give us a call at (866) 534-9725 or check us out online at

February 13, 2021