How to Determine the Stain on Your Pool

To determine what that ugly brownish staining is on the bottom of your pool, you can do a simple test to tell.
Some stains are caused by metals (copper, iron) that get introduced to your pool in many ways. Your local water supply can be loaded with metals. Using a copper based algaecide too much can introduce it. It can also come from "less quality" chemicals especially salt if you have a salt chlorine generator. If you get your salt from a big box store (Lowe's, Home Depot, Costco) it is not very refined. It may say 99% pure but what about that other 1%? It is usually full of minerals and metals that can have a major effect on your pool. Think of the amount of salt you put into your pool. That's a lot of 1% unknown stuff going into your water. Go to a pool store and purchase salt that is designed to work with salt generators. Trust me, the little more money spent up front will save you in the long run. Metallic stains usually effect the white parts of your pool first. The steps, the return and suction fittings, and automatic pool cleaners.
Cut a lemon/lime in half and rub on the affected area under the water. You can do the same with a granular pH decreaser or an uncoated Vitamin C tablet. If the stain immediatly either goes away completely or lightens a lot, then you have metallic stains. If the stains do not go away, then try the same with a chlorine tablet for only a few seconds. If this works, then your stain is not metallic and caused by leaves, dirt, or other organic matter. Fiberglass pools are notorious for metallic staining, so if you have a fiberglass pool and the entire pool is covered with brown, you probably have metals present. I have told you a "trick" that you can do with common household products to determine the cause now you can refer to my other articles for treatment of either metallic or organic stains