The two main stain categories are metal and organic based stains, which come in a variety of colors. These color combinations include green-brown, red-blue, blue-green-black, green-brown-red, pinkish-red, or brown-black-purple. Try to distinguish which color combination your stain is. [1] X Research source
Organic stains are typically green, brown, or bluish-purple. It may be easy to diagnose organic stains if you can see organic debris like leaves settled at the bottom of your pool floor. If an organic stain is suspected, try applying a small amount of chlorine directly to it. An organic stain will dissolve easily with a soft head brush, whereas a metal stain will stay put.
The metals that commonly cause pool stains are iron, manganese & copper. Copper is from ionizers and corrosion of copper and brass pipes. This will result in blue, green, teal, black or dark purple stains. Iron is from well water, corrosion of iron pipes and fittings and will result in rusty brown, gray or greenish-brown stains. Manganese is from well water and will result in pink, dark brownish-black or purple stains. Calcium comes from plaster, grout, mortar, or cal-hypo chlorine shock and shows as white crystals. [2] X Research source If you have a metal based stain, it is important to know exactly which metal is causing you problems in order to properly treat it. 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 metal stains from developing.
Use test strips at least once a week. Bring a sample to your local pool store once a month to have it professionally checked, especially when opening and closing your pool.
OTO chlorine is the chemical that tests for total chlorine. It’s a yellow liquid you add to your sample. The more yellow, the more chlorine there is in your pool water. Phenol red is a red chemical you add to a small sample of water to check the pH balance. The more red the water, the higher the pH balance is. With a liquid test kit, it’s hard to see the low end of the colors. Make sure you use a white background to examine the colors to be accurate.
If your fill water is acceptable, metals are most likely being introduced into your pool water through corrosion. Check all pool equipment for corrosion to make sure they are not leaking metals into your pool water.
If you have trees that hang over your pool, watch for leaves, branches, or fruit that may drop down into the water. You can use a pool skimmer to routinely clean out the debris. Any organic debris that floats to the bottom of your pool needs to be removed with a pool vacuum. You can use a hand-held vacuum or an automatic pool vacuum that uses a sensor.
Test the water to ensure the balances of pH and alkalinity are where they should be. The pH level should be between 7. 4 and 7. 6, while alkalinity should be between 100 and 150 ppm (parts per million).
After using your stain removing product, make sure you shock the pool so that you have a sufficient amount of chlorine in the water before it goes green from an algae outbreak.
Add an algaecide to the pool water. Be sure to follow the instructions on the product box regarding the method of application and how much you need for your size pool. This prevents algae from growing with lowered chlorine levels.
Treat large stains by adding ascorbic acid to the pool water by sprinkling it evenly over the surface of the water. Start by using a 1/2 pound of ascorbic acid per 10,000 gallons of water in the pool. Set the filter on “circulate” and turn it on. Allow the ascorbic acid to work for a half-hour. Check the pool to see if the stains are gone. If they’re still there, add more ascorbic acid, and let the filter circulate the treatment for another half-hour. Repeat this process until the pool is clean.
Do small shock treatments every week to prevent algae outbreaks. Scrub the bottom of your pool several times a week as a preventative measure.
Use a sequestering agents, also known as Chelators. They tie-up minerals in a solution which prevent them from floating free in the water causing stains. Just make sure they do not have phosphonic acids, as they break down into phosphates and can cause an algae outbreak. Disposable absorbent bags also remove and eliminate metals. Just drop one into your skimmer basket (or pump basket) and it will absorb metals such as copper, iron, manganese, cobalt, silver, and nickel.
Dark pool staining can occur from mudslides or mulch-slides into the pool. If you can’t prevent these materials from going into your pool, try re-coating your pool with a dark colored plaster or liner to help hide these types of pool stains.
