Stains usually don't happen overnight even though it can seem that way. Most stains manifest over a period of time when the pool water becomes unbalanced at which point its just waiting for excess organic and or metallic compounds to create stains. Similarly Scale is also indicative of your pool or spa being out of balance over a period of time. Incorrect pH, sanitizer, alkalinity levels, calcium levels, and water disposition (Corrosive or Scaling) help set the stage for stain-causing debris and metals to wreak havoc on your backyard oasis. Another scenario that causes irreversible damage is corrosive water seeking calcium to restore itself which can pull calcium from grout or plaster causing etching, mottling, and even buildup of calcium crystals. In salt pools using a chlorine generator, galvanic corrosion is much more likely to occur and can be the cause of many types of stains. The bottom line? Maintaining your pool or spa water properly is essential to maintaining your oasis. And your pool equipment!

If you don't ensure your pool is regularly cleaned including removing debris such as leaves, branches, berries, pine cones. etc. these materials can leave behind stains on the surface of your swimming pool. Organic debris staining is typically represented by brown splotchy stains in the shape of the organic matter that was left in the water. The stains themselves are predominantly caused by tannins found in the debris.

Untreated algae can cause speckling on the surface of your swimming pool and leave your pool or spa water with a green tint. The three most common types of algae are described by their colors—green, black, or yellow (although yellow algae is most often called mustard algae). Algae is easily kept out of your water by regular brushing of the surfaces in your pool or spa. The most likely spot for algae to start accumulating is that difficult to reach spot that often gets thought about and then ignored.

Black algae is by far the most damaging form of the three, and incidentally isn't actually algae, its actually dense colonies of cyanobacteria with chlorine resistant shells with roots that grow down into your underwater surfaces whether they are plaster, tile, or grout. This makes it the worst of the three for removal as it requires specialized attention not only on your underwater surfaces but in your pool pad equipment as well.

Metals are found naturally in pool water and their presence can be increased by leaching from other sources such as residential plumbing, fertilizers, and pesticides. If you live on a golf course or in an agricultural area where you get a fair amount of rain you can expect to have not only metals but fertilizers as well such as phosphates and nitrites. Iron, alumininum, zinc, and copper can also come from the hose you use to fill the pool. Additionally pool heaters often have copper heat exchangers that will degrade and become soluble if you allow your water to remain in a corrosive state. Algaecides are one of the most common sources of metals in your water. The problem with metals is that they do not evaporate like water does so the concentration of metals builds up over time each time you use algaecide or fill your pool. When the saturation point is reached, pool water is unable to contain additional metal this happens in winter more often than summer because warm water can hold more dissolved solids including metals than cold water can because increased temperature leads to faster molecular motion and more effective interactions between the water and the dissolved substance, in this case, metals. This is when metals start to fall out of solution and relocate themselves on surfaces of your swimming pool or spa, thereby creating stains that seem like they popped up overnight. The color of the stain can often give you an indication of what the stain composition.

Here's a quick recap:

• Green algae: stains are usually represented by green-tinted pool water and a green speckled pool surface.

• Mustard or yellow algae: is most often represented by light brown and yellow colors. Think of the Mustard selection in your local market and you'll understand why most people call it mustard algae which most often grows in shady areas of the water.

• Organic Stains: will most often leave an stain in the shape of the offending debris, usually brown in color although colors can vary depending on what the organic material is.

• Black Algae which again is not actually algae but a colony of cyanobacteria, tends to form black speckles and clusters often in circular shapes that will grow roots into the surface of your swimming pool.

• Iron: Stains ranging from yellow and orange to reddish rusty and dark brown color. Iron stains can be mottled and cover large areas or be dark and in small areas depending on how the iron is introduced into the water. If you (or your neighbor’s kid) throw metal into your pool iron can tend to stain in a similiar pattern as the object such as a nail or staple etc,

• Oxidized copper: stains in a pool or spa , often appear as blue-green, gray, or brown stains and are caused by the oxidation of copper in the water, which can come from various sources like pool equipment, chemicals (especially algaecides), or even the water itself.

• Copper: this type of metal can tint pool water blue before stains form on the pool’s surface. These stains are commonly blue-green in color but can also appear gray, black, and brown although if your cyanuric acid levels are to high, copper stains can also appear as purple.

• Manganese: found in well water in some regions, this metal leaves a purple tint in the water with brown, black, or purple stains on the surface of the pool. Although not prevalent in the Rogue Valley it is often found nearby in Crook and Lakeview counties, so never say never.

• Cobalt stains are less common but if you have a fiberglass pool or spa you can also find yourself dealing with cobalt staining or cobalting. Cobalt Stains appear as grey-black spots and are caused by cobalt leaching from the resin which was used to make your pool or spa. Most often seen as smaller dark black stains that appear wherever water penetrates the gelcoat and reacts with your pool or spa water.