Absorbic Acid Treatment

[Nanos203]

Hello! A couple of years ago I purchased a home with a pool that had significant staining. Last year I had the pool drained and acid washed; staining was greatly reduced but there’s still some residual. I’d like to do an absorbing acid treatment and then drain the pool again (I don’t want to have to deal with sequestering agents). It’s the beginning of the season here so I just pulled off the pool cover today and opened the pool. I’ve brushed and vacuumed the pool and brought the pH down to 7.2. I haven’t slammed or added any chlorine so the water isn’t clear. Do I need to get the water clear before treating? I’m guessing I don’t since the absorbing acid will eat the chlorine anyway but wanted to check with the pros here. FWIW, water temp is 52.

Thanks for any advice and pointers!

 

[Texas Splash]

I have to ask a basic question ..... this staining, are you sure it's from metals? Iron or copper? Since you drained and acid washed, is there any chance it was just organic staining? If you're not sure, do the following spot tests on some stains:
- Vitamin C tablet = iron (rub directly or place some crushed in a thin sock)
- Chlorine tablet = organic (rub continuously, do not let sit in one spot)
- Dry acid = copper (place some in a thin sock and rub on the stain)

Normally yes, we normally recommend doing a SLAM Process first to kill all algae and achieve good water clarity before running the AA. If you do the AA first, then the elevated FC level of the SLAM can cause residual metals to react. HOWEVER - you do plan on changing water right? So technically you could do the AA first then just change the water, but the challenge there would be water clarity. If the water is mucky or green from algae, you might not see well enough to monitor the AA process. Since your water temp is still chilly, you should have good success doing a SLAM Process. It ight feel like a waste of chlorine since you're going to change the water, but really your call depending on how well you can see the pool surfaces if you go right to the AA.

Ascorbic Acid Treatment - Further Reading

www.troublefreepool.com

 

[Nanos203]

Thanks for the quick help. If I do the AA treatment and it doesn’t do anything or enough to warrant a drain— will it be a problem to SLAM afterwards? My water currently has 0.1PPM iron and 0.2PPM copper.

 

[Nanos203]

Thanks for the quick help. If I do the AA treatment and it doesn’t do anything or enough to warrant a drain— will it be a problem to SLAM afterwards? My water currently has 0.1PPM iron and 0.2PPM copper.

@Texas Splash how long can I leave the pool in an AA state? Also, if the stains don’t lift (which they haven’t), can I go ahead and do a no drain acid wash directly after the AA treatment?

 

[markayash]

When you do the AA your FC will tank. So it may get a lot worse. Is it clear enough to see if the stains lift?
I don’t think leaving the AA in will do any damage just be careful you don’t create a swap mess

 

[Texas Splash]

how long can I leave the pool in an AA state?

Probably longer this time of year than folks down south with warmer water. No specific time duration as much as visibly seeing the stains lift. Getting algae is usually the biggest concern because of the zero FC level. But if in doubt at all about the source of staining, be sure to do the tests noted above. An AA treatment "should" resolve (lift) a majority of any iron staining unless the staining is protected by scale. That can happen with organic staining as well.

If you believe a no-drain is required, be sure to check to see if a rebalance would be in order. You want good predictability of the pH/TA before you start, and the no-drain definitely can present some problems if not done carefully. If you end up trying a no drain, I would start a new thread about that subject just so our experts can focus on that issue alone.

 

[Nanos203]

Thanks everyone. Will start a new thread as I’m a bit stumped with my stains and need some expert guidance.