irritating brown stains

[gatorwayne]

First off the numbers. I test chlorine/PH every couple days to see when the next cup of acid needs to go in. I test the water monthly with my kit and visit the pool store every weekend or two. These are the numbers from today. They are very close to what I usually have. The only number that has fluctuated is calcium hardness. Earlier in the spring it went over 400 for a few weeks before I realized the importance of getting it lower. I have been draining and filling to get it down. Mother Nature has also helped this summer with lots of rain. Whenever I drain the pool I go get the water tested to make sure it is balanced. Pool gets brushed once every week. I bought a wall whale brush when this problem started.

FC: 4
TC: 4
CC: 0
PH: 7.4
TA: 75
CH: 305
CYA: 60
Borates: 35-40
Salt: 3300

My wife and I went on vacation May 1-12 and our children were supposed to throw a cup of acid in the pool every couple days. That did not happen. We returned to a pool with a PH above 8.2 and CH around 430 or so. Chlorine has never been a problem as we have a SWG. I just adjusted it down as the FC level was averaging 5-6. This is when I discovered the little brown spots. They are brown in color like dirt and a bit stubborn to remove. I started using a stainless steel brush because the nylon brush was not working. I lowered PH to around 6.6 for one night and scrubbed away the next day, raised the PH, and thought with water now in balance I would be done with them. That was 6 weeks ago and today I spent another 15 minutes scrubbing spots.

They only appear on horizontal surfaces. They do not cluster at all and appear completely random around the pool. They are reoccurring but their numbers are greatly reduced since I balanced the water. I’m just wondering what else I might do to stop them from coming back.

 

[JasonLion]

Try placing a vitamin c tablet on one of the brown spots and see if that does anything. If it removes the spot they are iron stains, presumably from the high PH. If not, we will have to try something else.

 

[gatorwayne]

Try placing a vitamin c tablet on one of the brown spots and see if that does anything. If it removes the spot they are iron stains, presumably from the high PH. If not, we will have to try something else.

I will certainly try that. I would jump in now if I had a vitamin C tab and it was not rumbling in the sky overhead. I considered trying this and even had a bottle of vitamin C in my hand two weeks ago but I don't know where the iron would come from. I only use my city water to fill and according to the report has no iron and only a very small amount of copper. All our pool toys are plastic or noodles. Nothing metal except the aluminum pole for brushing goes in the pool. Where does the iron come from?

I will get some vitamin C tabs tomorrow and grind a few into some stains. I'm certain I missed a few today.

 

[gatorwayne]

I bought some vitamin C today and held some of the tablets against a few spots as well as rubbed some tablets on the spots. No changes to the spots. I did notice some of the spots seem to be in very slightly pitted areas.

What should I do next?