Hi...first post, have read , and used, information from here for the last two years...still learning.
20,000 gal vinyl pool 12 years old.
have a pool heater,
water:fc 3, ph, 7.6, ta 100, cya 50, ch, 310, , water is clear.
Live near the beach if that matters. with all the rain lately, the ph sometimes goes down, and have used borax (as suggested on the posts) to raise the ph. works the way it should.
Here is the problem. a couple of weeks ago, after having used borax one morning, discovered the next day dozens of small 1/4 to 1/8" round, or slightly round, copper colored marks in the fiberglass steps. (I mention the borax, because that's the only occurrence of addl chemicals I can think of different than the usual). I believe I put the borax in the deep end, but may have put it in at the step area as well.
Living near the beach, (and with 2 grand kids) there always seems to be some sand around the steps. not lots, but some. don't know if there is some interaction chemically there?
I tried the vitamin c test, no success. (I did notice some metal discoloration near the deep end the week prior, did the stain free, metal out this week, cleared the discoloration in the deep end, nothing to the steps) I also put the stain free right on the steps to add to the pool.
I have even tried a magic eraser to no avail.
Help! looks yucky