The brown staining in your pool is caused by oxidized iron, which is probably getting in your pool from the well. The oxidizer in E- Z POOL shocks out more contaminants than regular chlorine shock. Sometimes, especially pools filled with well water, this can cause an issue that was previously unknown while on chlorine because it is not as versatile as the E-Z POOL®. In most cases, the problem can be fixed rather easily.
When you used ascorbic acid before, it was the right thing to do, unfortunately you weren’t told that the job was only half done. Ascorbic acid removes the stain rather easily BUT once the stain is removed, the molecules that formed the stain are still in the pool water. They have just been dissolved. Unfortunately sand filters only filter out particles that are 20-25 microns and larger, oxidized iron is in the 2-4 micron range. So, your filtration system needs help removing the particles that caused the stain out of the pool water. The fastest and easiest way to do this would be to:
1. Treat your pool with ascorbic acid, you shouldn’t need more than a pound. It should work within an hour or two. Once it has been circulated throughout the system.
2. Once the brown stain has been lifted, turn off the pool pump.
3. Spray a 16oz bottle of Revive (removes the iron particles by dropping them out of solution and in to a sediment on the bottom of the pool so you can vacuum it to waste, removing it for good) over the top of the pool.
4. Leave the pool off for at least 24 hours.
5. Vacuum the debris out of the bottom of the pool while your sand filter valve is on waste.
6. Follow the weekly directions for the E-Z POOL® that your local store has given you.
You should also have a bottle of Revive! at the house for whenever you fill up your pool due to evaporation or splash out. Simply attach the Revive to the end of your fill hose and spray the product over the top of your pool water, covering the pool twice, Revive! will capture the particles from your well water that shouldn’t be in your pool water and send them to your filter for you so that you do not have to go through this huge procedure over and over.