This is our third season for our fiberglass pool. The past 2 years, when we opened the pool, there were quite a few leaves in it. We got the leaves out, balanced the chemicals, and had clear water and a clean pool for the summer...no staining. This year, we opened the pool, got the leaves out and found that nearly 2/3 of the pool surface is stained...kind of a yellow/green/brown color. The staining is in all areas of the pool with patches of unstained areas. Brushing it does nothing.
Test results after opening:
Salt 2200 (added 2 bags, now at 2900)
At first I thought it was algae. I tested and found .5 CC...hardly a high reading, but I had always had 0 in the past. So, I got the chlorine up to about 11 and kept it there for a few days. The stains remained, but the CC was down to 0. So, I guess it's not algae.
Over several days, I lowered the FC down to 1. Still had a CC of 0. I added 1.5 lbs of Stainfree a couple of hours ago. I have tried brushing and don't see any reduction in the stain.
My current readings are:
CYA 30 (keeping it low to get FC low for Stain Free)
We have city water.
I know I am supposed to vacuum 24 hours after putting in the Stainfree. I'll give it 24 hours to fight the staining. If the Stainfree doesn't work, I don't know what to try next.
What could be the cause of the staining?