Help. Citric Acid Treatment Not Removing heavy stains

[hokierick]

I have 9-year old plaster/gunnite 15K pool with very heavy iron staining. I put bottle of sequestrant in monthly but doesn't help.

Normal test results are PH=7.4 to 7.6; TA=70; CH=240; CYA=60; FC=9 to 11; CC=0. Water source is well with high iron and 8 pH. I understand the relationship between high chlorine, high pH, and staining. Think that has been part of the problem. Will do a better job of appropriate FC level, CYA/FC balance, and keeping pH closer to 7.2. Just have to remove the stain first.

I am in the middle of putting citric acid to try to free up the stains. I put the acid in a sock and tested a very stained area in deep end of the pool. Didn't get it all but it did work. Then used sodium metabisulfate to reduce chlorine level. It was at zero yesterday when I started this. With pool on recirculate, I put in 2 1/2 pounds of citric acid around edges of pool; concentrating on deep end, where staining is terribly dark. No obvious removal after 6 hours. I put in another 2 1/2 pounds and still no obvious stain removal. I still have the pool on recirculate and haven't put in any sequestrant yet, because others said you want to wait until the stains are gone before doing that.

Pool temp is 65, pH is now so low I can't measure it, FC is zero, and no amount of scrubbing, brushing, or cussing has helped.

Looking for help with next steps. Also wondering if I have to worry about organic issues since FC is zero...even if pool temp is below 70. Was also wondering if cool pool temp negatively affected citric acid working. Many thanks. rick

 

[JasonLion]

Welcome to TFP!

The cold water will certainly slow things down, though it should still work. You want the PH down around 7.0 to 7.2 during the removal process. If the PH is higher than that, try lowering it.

If you haven't already, I suggest adding some algaecide to help keep algae from starting. We recommend using polyquat based algaecides.

How well things work, and how much citric acid you need, depends on how much metal has been deposited on the walls, which is difficult to impossible to determine in advance.

Have you read through the AA treatment topic? There are various hints in there, though none of them obviously apply to your situation.

One good double check would be to use some more citric acid in a sock on a new limited area and see how that goes. If that works, then things are just going slowly and/or need more citric acid. If that doesn't work then something more complex is going on.

 

[hokierick]

pH is way below 7.0. Do I need to try to bring it back up to 7.0?

Did citric acid in sock thing again. Definitely takes some of the stain off but not close to all of it...and only in exactly the area where the sock was. It has very heavy staining.

I didn't put in polyquat based algaecide, but just added some. Thanks.

I thought 5 pounds of citric acid was a lot, but when I got no results with 2 1/2 pounds, I went "double or nothing." Got nothing. I don't have any problem adding more, but I don't understand consequences if it still doesn't work and I've overloaded the pool with citric acid. I have plenty left.

I did read AA treatment. Took what I thought were all the hints for my situation.

Will it hurt to just let it stay on recirculate for another day or so to see if it finally starts working, should I put in sequestrant now or wait, or should I continue to put in more citric acid?

I really appreciate your help. Charting new territory for me. rick

 

[JasonLion]

The more metal that has deposited, the more citric acid and the more time the process takes.

Leaving the pool for 24 hours is fine. The only risk is slightly increased odds of getting algae. The more citric acid you use the more chlorine you will eventually need to add to neutralize it, but otherwise it isn't a problem.

Don't adjust the PH right now. If the PH was high you would want to lower it.

 

[hokierick]

Ok. I won't panic.

I'll leave it on recirculate tonight and tomorrow and see what it looks like after I return from work tomorrow. If still no luck, I'll add a couple more pounds of citric acid.

I added algaecide. Now I'm wondering if I added enough. I put in about 6 ounces for 15K pool. Should I up that amount because of zero chlorine?

Thanks again. I really appreciate the support.

 

[JasonLion]

I'd put in at least double that amount of algaecide, though tomorrow is soon enough.

 

[hokierick]

Thanks. I'll let you know how it turns out. Again, I appreciate the advice.

 

[Swampwoman]

What kind of surface is your pool? I've had similar incomplete results during my autumn treatment with cold water, just so you know.

 

[hokierick]

marcite suface over gunnite. Pretty rough. BTW, just home from work and checked pool. Still heavy staining everywhere except where I did the sock test. Both areas clean. Makes me wonder if I need to add more citric acid (already at 5 pounds for 15K) or add sequestrant now and see what happens. Appreciate your thoughts and guidance.

 

[Swampwoman]

I did read somewhere on one of the many AA treatment threads that Citric Acid is less effective/requires more than Ascorbic Acid. But I had so-so results with Ascorbic Acid. I would definitely add more and wait longer, so long as you add lots of polyquat to avoid algae.

 

[hokierick]

Thanks. I'll add more polyquat now. Up to 12 ounces.