What Are Dark Marks On Fiberglass Lining?
by Calvin
A few months later there are dark patches (darker blue/blackish) appearing in one area only. Could this be caused by a low pH or what could be the reasons for this? Thanks for the question Calvin My first guess would be a metal problem, probably iron, copper, or a combination of both. You can take a sample of your pool water to your local pool store for analysis. If it is iron, one of the best ways to handle this is with ascorbic acid, which is nothing more than Vitamin C. After an ascorbic treatment, you'll want to use a metal sequestering agent. This is a chemical that binds with the metals (the metals that come off the surface of the pool after the ascorbic treatment, or metals that are already in the water). Some good metal sequestering agents are Jacks Metal Free and Metal Wizard. These agents won't get rid of the metal, but it keeps it in solution, or suspension, until it can get filtered and backwashed out. The purpose of ascorbic acid is to remove metal stains, especially iron. You should lower the free chlorine level in the pool to 1 ppm or to zero. It's best to add a PolyQuat 60 algaecide before letting the chlorine drop in order to prevent algae. Normally the dosage for ascorbic acid is 1 lb. per 10,000 gallons. You should run filter 24 hours and backwash or clean after 2 days. Test the stain first with a Vitamin C tablet before adding ascorbic acid. Ascorbic acid may not work for all stains so you'll want to test first to see what type of reaction you will get. Amazon has good prices and you can go here to purchase your ascorbic acid: Pool Supplies Go to Amazon and type in ascorbic acid for pools. Hope this helps and have a fun and safe swimming season. Robert |
