Chlorine levels after OA iron treatment

PoolFunYikes

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May 19, 2020
24
New Hampshire
Hi, I’m a relatively new pool owner (1yr) looking for some advice on what went wrong with my two attempted Iron stain treatments and how to fix the now strange chlorine levels. Sorry for the lengthy post but it’s a complex tale....

I have a 10,000 gal salt pool with SWG that had iron stains when I moved in last March 2019. I made the Iron ID with a Jack’s test kit. In Sept 2019 I went into a Jacks #2 treatment (OA) and it worked wonders, turning the pool bright white. My big dilemma was that I didn’t have a good feel for how slowly to add chlorine and ended up adding a about 1 gal 12.5% liquid per day for a few days and could not register FC. By the time I was able to get FC to register, I had used about 4 gal. I had the water tested at a local pool outfit that said I was at 30ppm CC and around 1 ppm FC. Their balance SW recommended adding a whole lot more chlorine to break the CC, but I was extremely hesitant to do so and instead waited it out.

I have read that OA consumes chlorine, but was not expecting it to show up with such a huge CC level . The rep at Jacks said it was due to the nitrogen from the OA and said I should treat the CC level as if it was the FC level. This I found was too hard to stomach since I have no idea what the mix is of sanitizing effective chlorine vs. spent harmful chloramines.

Here is the dilemma of inconsistent chlorine readings I was faced with:
1. Pool store A test 20-30 ppm CC, 1-3 ppm FC
2. Different pool store B did an OTO test and said 0 CC, 3ppm FC
3. Home Test strip shows 3 ppm TC, 0ppm FC
4. DPD1 home test was 3ppm FC

With no noticeable chlorine odor and clear water, I went with #2 and #4 from the list above thinking the OA was somehow interfering with Store A test method and that my strips were similarly not compatible with the post OA treatment state of the water. We swam for months without irritation and I used DPD1 tests alone to keep FC levels good with the SWG. The iron stains reappeared within a couple weeks of OA treatment which I chalked up to me not adding the chlorine in slow enough.
Fast forward to Feb 2020, the stains are annoying me so I try again. This time I was very careful about using right amount of Purple stuff sequestrant, putting a CuLator in to hopefully capture the metal, and very slowly adding the chlorine and get back to the point where I have 3ppm FC again on my DPD1 test. Within 3 weeks Stains reappeared but even worse than before... like a coffee cup.
I finally ordered a Taylor DPD-FAS test to see if I could independently measure the CC and see where I stood.
My readings now are:
1. Home strip: 3 ppm TC, 0 ppm FC
2. DPD1 tablet home test: 3 ppm FC
3. Taylor DPD FAS test: 10 ppm FC, CC out of 20 ppm range!

Im super confused and frustrated with the after effects of the OA on the chlorine levels and test results. Also very frustrated that the stains reappeared so quickly which I assume is related to the very high chlorine levels.

Before I started this whole OA debacle last Sept, chlorine was spot on...CC was near 0 and FC at 3ppm per a Pool store A report. Staining was not pretty but at least lacked the high contrast tan waterline mark I now have formed in the past couple months.

Any ideas on how to explain the chlorine readings and how to bring CC to 0 and FC in range? Also Id love to be rid of the stain, but not sure how since both attempts ended in a more prominent restain.
 

ajw22

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Jul 21, 2013
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Jacks #2 is Sulfamic Acid. Read Acid - Sulfamic Acid

It had taken members months of SLAM level FC to clear CCs after using Jack's Magic #2 Copper and Scale Stuff.

Read...

 

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
Thanks ajw22, sounds very much like my same problem. I’m confused by the OA vs Sulfamic... the Jacks technical support had said Copper and Scale stuff #2 was Oxalic Acid as did the 10lb bucket it came in. Is it some proprietary blend that closely resembles both of these compounds? Either way the behavior matches what is discussed in that other thread. Guess I will try shutting off the SWG and waiting it out
 

ajw22

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You say you identified iron stains. Ascorbic Acid is normally used to lift iron stains. Ascorbic Acid Treatment - Further Reading

Jacks #2 is used in copper stains- Copper in Pool Water - Further Reading


@JoyfulNoise thoughts on Jacks #2 being Oxalic Acid vs Sulfamic Acid & CCs?
 

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
A little more info on the treatment.... The stain kit showed Iron. I followed the iron treatment from Jacks which first prescribed removal of scale through a #2 treatment of Copper and Scale stuff. The next step was supposed to be the #1 Iron and Cobalt etch, however the stains completely lifted after the Copper and Scale treatment. I consulted the Jacks tech and he said I should skip the Iron Cobalt treatment if the #2 treatment was sufficient. But unfortunately it all restained...
Do you think the restaining occured because I let the CC get so high 20-30ppm as I watched FC instead?
 
Last edited:

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
also I should mention the staining is accompanied by some scaling. This despite keeping the pH around 7.2. I can feel the scale as the pool surface has a slightly rough surface . It smoothed while pH was dropped during the Jacks treatment, but came back. Could I possibly be fooled into thinking my pH is 7.2 because of the very high CC?
 

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
Jacks #2 is Sulfamic Acid. Read Acid - Sulfamic Acid

It had taken members months of SLAM level FC to clear CCs after using Jack's Magic #2 Copper and Scale Stuff.

Read...

That other thread showed the owner had no CYA. I have the same condition. CYA = 0, repeated the DPD-FAS today and showed 7 ppm FC, > 25 ppm CC (stopped at 50 drops on 0.5 ppm scale since exceeded the 20 ppm test range)

should I just wait at this point or should I add CYA to get it back to 70 ppm, and SLAM? I don’t understand if the CC will come down on its own with normal 3ppm FC levels or should I add more chlorine to achieve SLAM Levels?
 

ajw22

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You should consider your chlorine level as FC + CC so your chlorine is around 32 ppm.

pH tests are unreliable as FC gets above 10 ppm although it tends to read high with dark burgundy color. I don;t know how the high CC effects the pH test.

I would suggest you get a pH meter and calibrating solutions. Like...


You need to calibrate the pH meter often and keep the calibrating solutions fresh. But it will not be affected by your funky water.

Add CYA to the pool. I would bring your CYA to 40. Maintaining higher FC+CC levels will eliminate your CC's quicker. SLAM FC for CYA 40 is 16 and I would keep your FC+CC in the 12-16 range. That is safe to swim.
 

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
You should consider your chlorine level as FC + CC so your chlorine is around 32 ppm.

pH tests are unreliable as FC gets above 10 ppm although it tends to read high with dark burgundy color. I don;t know how the high CC effects the pH test.

I would suggest you get a pH meter and calibrating solutions. Like...


You need to calibrate the pH meter often and keep the calibrating solutions fresh. But it will not be affected by your funky water.

Add CYA to the pool. I would bring your CYA to 40. Maintaining higher FC+CC levels will eliminate your CC's quicker. SLAM FC for CYA 40 is 16 and I would keep your FC+CC in the 12-16 range. That is safe to swim.
Thanks so much for your help. The reason I ask about chlorine impact is that the 1200-V pH test has a chlorine neutralization step .. 1 drops for < 3 ppm FC, 2 drops for > 3 ppm FC. I didn’t know if that test assumed CC is near 0 and FC is less than 5. I just did a test to add more than 2 drops of the sodium thiosulfite. I added 5 and my pH was 8.2! So I think I answered my question... the 7.2 pH was erroneous due to high chlorine and required more than the standard dose of neutralizer. Do you know if the Harris pH meter has the same need to neutralize chlorine before testing?
 

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ajw22

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Jul 21, 2013
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Northern NJ
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pH meters are not sensitive to chlorine levels.
 

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
Jacks #2 is Sulfamic Acid. Read Acid - Sulfamic Acid

It had taken members months of SLAM level FC to clear CCs after using Jack's Magic #2 Copper and Scale Stuff.

Read...

So I think I misinterpreted your SLAM FC level recommendation. I tried maintaining approx 15-20 ppm FC for the past two days, and ended up using 5 gal of liquid 12.5% shock to do so. I was assuming that SLAM level would help drop the CC. I also ordered a 16oz bottle of the DPD-FAS so I could finally see the CC test through to completion. I had to dilute 2:1 with distilled water and came up with 18 FC and 110 ppm CC!! Yikes. I see the Sulfamic acid is making the shock go straight to CC. How does this cycle eventually end? Should I just hold tight, remeasure daily and wait for the chlorine CC to disappear. And what eventually will clear the Sulfamic acid from the pool?
 

ajw22

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There is no easy answer for your problem. You have polluted water. It has taken months for the CCs to clear for some folks. Only continuous doses of chlorine will clear the CCs that are being formed.

You are in a tough place since you don't want to drain a fiberglass pool. Dumping the water and starting fresh would make the problem go away. The No Drain Water Exchange Process would let you dilute the polluted water at the expense of lots of water.

Let's see if we can get the attention of @JoyfulNoise or @mknauss
 

mknauss

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If the stains you used the Jacks stuff for are gone, now is the time to exchange water to fresh to rid yourself of metals. I assume these were copper stains?

See Draining - Further Reading
 

PoolFunYikes

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May 19, 2020
24
New Hampshire
Well I thought they were iron scale based on the Jacks ID kit, but maybe copper. They do clear if I put MA right on them, so not sure if that helps. At this point I don’t care too much about the stains and just want the CC issue gone. What a terrible pain, definitely not doing Jacks #2 again. When you say I can’t drain a fiberglass, are you referring to the risk of damage from pressure of the ground water and backfill ?
 

JoyfulNoise

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May 23, 2015
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Jack's Magic #2 stain remover has always been sulfamic acid. Not sure why the person at Jack's is telling you it's Oxalic acid unless they have changed their product line. You should clarify exactly what it is you have put in your pool.

If it is sulfamic acid, then your pool water is "hosed" for a good long time. Chlorine reacts with sulfamate to form both monochlorosulfamate and dichlorosulfamate. As well, adding more chlorine in the water only increases the amount of dichlorosulfamate. Both MCS and DCS register as CC's on the FAS-DPD test but they are not true sanitizers and are too slow to be considered sanitizer. So your water is probably fine in terms of CC and all you can do is measure FC and work with that. You'll have to ignore CC's until you have exchanged enough water to lower the sulfamate contamination OR when the chlorine has had sufficient time to oxidize it. It can takes months for the sulfamate to get oxidized into nitrates and sulfates so you are better off if you can remove water from your pool and replace it with fresh water.
 

PoolFunYikes

Gold Supporter
May 19, 2020
24
New Hampshire
Thank you so much for your help. I threw the Jacks empty bucket away but distinctly remember the tech saying Nitrogen from the Oxalic acid was the problem with my chlorine levels. Now that I see there is no N in the OA molecule I assume he must have made a mistake and you are correct. For future reference... would the Sulfamic acid have left the pool on its own earlier if I had maintained TC at around 3ppm in the first place vs adding the chlorine and creating lots of DCS? Or would it have just prolonged the problem. I.E. Is the Sulfamic acid now even more locked into the pool due to being converted to CC? If I follow the guidance to ignore the CC level and watch FC do you think the DCS will eventually oxidize out over the course of a few more months? Hate to have to drain/exchange unless necessary
 

JoyfulNoise

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Sulfamic acid added to chlorinated pool water forms chlorosulfamates, there’s no way to change the way you add it that makes any difference. Sulfamates are very slow to breakdown and the addition of CYA to the water will slow it down further. You still have metal ions in the water, they are just dissolved at the moment and will cause staining to return over time. Your best approach is to drain and refill as best you can.
 

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