(cross-posted from Aboveground Pools)
I am a relative beginner to pool chemistry. I bought a house 2 years ago with a 21' round old above ground pool with a new liner. I am able to shock and use algecide to get rid of algae and get the water clear, but this year when I opened the pool (Georgia, Southeast USA) my kids said the water "tasted funny". Not that they should be tasting it, but...
Anyway, I tested the water and Ph was low off the scale. The test shows light yellow (below 6.8). I bought a 10 pound bag of Arm and Hammer and added a pound at a time over the weekend until it was gone, but it only turned a little darker yellow on the test. The TA test shows about 50.
However, even with the still low Ph, when I added the baking soda, the bottom and sides of the pool stained badly. Ugly yellow steps (were white as snow) and an ugly yellow ring and ugly yellow stains all over the bottom. This stain will go away when rubbing Vitamin C on it, but it comes back the next day. It is not orange or brown.
Should I be getting this staining even with the Ph that low? I lowered it back down to see by putting in a pound of Ph reducer, and the stains went away again, but this can't be good.
I also let the Chlorine go to 0 and put in two quarts of Metal Out and ran for a couple days, then raised the Ph back up, still ugly stains came back.
What am I doing wrong?