Ascorbic acid surprise.

I have a 4 month old gunnite pool, 20,000 gls with brownish stains on the walls, bottom and steps. I suspect they are from a copper algaecide I foolishly put in several weeks ago. The stains responded to the vitamin c test and to dry acid pH reducer in a sock, so I opted for an aa treatment.

Numbers this morning via Taylor 2006A kit:

FC 3
CC 0
pH 7.4
TA 90
TH 175
CYA 70

Chlorine was trending down nicely the last few days with none added; FC was 8 on July 15. CC has been 0. Added thiosulfate this morning to wipe out the chlorine. Cartridge filter removed. Left pump off while putting in aa so it could sit on steps and swimout for a while. Came back 1 hour later and pool water was clear GREEN. What? Added 2 quarts of Jack's Magic Pink stuff and started the pump, no filter.

FC now is 0 and pH is about 6.8. The pool now, 3 hours later, is still a clear but darker green. Is this an algae bloom? I don't think it is as there was no sign of algae prior and the water is clear, no clouding. I plan to start adding back chlorine via bleach tomorrow I guess. Could this be copper or iron releasing into solution causing the water coloration? One more thing, I added a Culator on Monday and this morning (Wednesday) it had turned blue indicating that it was binding copper per their literature. At this point some stains have lifted but not a miracle yet. Plan to brush tonight and hope for better results by morning.

Surely hope to hear from the aa treatment experts on here. Tried to post to stain removal thread but had to go here first since I am new. Great forum; I have learned a lot as a lurker.

If you have clear green, that's probably the copper precipitating out. You can log out to read through the Metals forum until your registration is upgraded, but I'll ask Marie (the resident stain expert) or Ben (the other expert) to pop in and see if they can help.

Janet

Curious --- why did you add the thiosulfate?

Welcome to the Pool Forum, by the way!

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Originally Posted by aylad

Ben (the other expert) to pop in and see if they can help.

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Ben who? ;)

Added sodium thiosulfate to burn out remaining 3 ppm chlorine. Thought that was part of the procedure else aa burns off the chlorine.

Ascorbic acid does not work the same on copper as it does on iron. It does seem like te ascorbic acid lifted the stain off the pool surface and is now in the water. You will have to get it to oxidize out to stain on your filter, but I am not familiar with cartridge filters, or copper stains. My advice would be to go on the Jacks Magic website. They have a lot of info about stains. They will probably tell you how to get rid of the green water using their products. Please keep us informed.

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Originally Posted by sweep49

One more thing, I added a Culator on Monday and this morning (Wednesday) it had turned blue indicating that it was binding copper per their literature. At this point some stains have lifted but not a miracle yet.

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If the Culator is turning color, then it looks like it's working--please, before you get rid of it, take pictures--both of the outside and inside. We're still researching this to make sure it does everything it claims to, and all the documentation we can get helps! If you can take pics, send them to poolforum@gmail.com, and reference this thread, or at least your username.

Thanks!

Put the filter back on and added a 3rd quart of the Pink Stuff last evening. Water is clear and colorless this morning. Little improvement to the major stain areas except for the top step where I sprinkled aa directly. Will take some pictures of the stains and Culator later. Now to work on getting FC and pH back in order.

BTW I looked at Jacks Magic website and yes they have some stuff for removing copper stains but it would be expensive. Pool contractor said he would drain and acid wash the pool for $300 + $80 for refill water; cheaper than Jack's treatment. Don't want to do that but when you see the stain pictures you will understand my frustration.

You may already know this, but in case you don't ------- acid washing removes the top layers of your pool's surface making them more porous and vulnerable to staining.

I noticed that your calcium is a little low for a gunnite pool. It should be at least 250. Sometimes ascorbic acid will lower calcium too, so you should check it again. You may want to try putting ascorbic acid in a sock so you can concentrate it on the stain. Just rub it where the stain remains to see if it lifts. let me know if it works, thanks