Help interpreting FAS-DPD FC/CC test results **Sorry, long, techy post**

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Originally Posted by waterbear

The amount of DPD powder is not critical as long as the pink color forms. If you are using a 10 ml sample one scoop is more than sufficient and often is with a 24 ml sample also.

If there is very high CC it is common for the color to return to pink on FC part of the test. The sample will also return to pink if allowed to stand. This is normal behavior.

Also, the pink will not return if all the DPD has not dissolved since there would be no more chlorene for it to react with once the titration is complete.

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Ah, I stand corrected. Thanks for the clarification.

Out of curiosity, this evening when I tested my chlorine level (I always use a 10 ml sample), I did it twice; the first time using my usual 2 scoops, the second time using 1 scoop. Oddly, I got slightly different results; 2 scoops FC = 4.5, 1 scoop FC = 5 (samples were taken from same location in the pool).

Anyway, like you said, it's apparent I can use 1 scoop instead of 2 so I can get many more tests out of the same DPD powder bottle.:)

0.5 is inside the error margin of the 10ml sample test - 4.5 and 5 are the same.

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Originally Posted by BigDave

0.5 is inside the error margin of the 10ml sample test - 4.5 and 5 are the same.

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Ahhh...I see.....that's good to know.

Thanks.:)

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Originally Posted by waterbear

I am a bit confused why you are constantly aerating and why you keep adding borax when your pH has not tested too low. What else are you trying to accomplish besides eliminating CC? ....

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I've had Alk of +250 for 4 years and Ben helped me lower it to 90-100 last month. The instructions for reducing Alk say to add Borax to raise pH from it's 7.0 level and to keep aerating until you reach your desired pH. (so that Alk won't rise along with it.) The problem is....as I was reaching my desiered pH level, I was also dealing with a lingering 1.0-1.5 CC. Ben had advised I raise my pH to 7.8 and keep it there as it helps get rid of the CC quicker. In doing so, my Alk began to rise also. I haven't added Borax for 12 days now. My beautiful Alk is MIA - it's been between 170 and 200 for the past 11 days so I haven't stopped aerating for fear it will return to 250s again. Alk tests 200-250 every time - but before the cya correction is applied. With pH slide up/down btwn 7.6-8.2 and CYA 70-90 during this whole process, the corrected Alk varies as well.

In addition, I was also trying to reach 50ppm Borates and the process of lowering Alk and then raising pH had brought it to 50 ppm all on it's own. Oddly, it rose to 80 ppm after I quit adding Borax. I haven't finished my reading up on the Borates thingy, so I don't know if that's a problem.

As we stand today, we've maintained 7.8 pH, corrected Alk is btwn 168-195, we've been maintaining FC at shock levels and we finally hit .5 CC on June 3rd. I still have to check it this morn to see if it lasted longer than 24 hours. Borates are 80 ppm and CYA is mysteriously at 90 again without having adding anything but bleach since the beginning of May.

Testing is much, MUCH better and I haven't had the recurrence of my changing sample color during FC since I reached 25-28 ppm FC and was able to keep it there. My previous testing definitely did not behave the way it does now.

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Originally Posted by waterbear

.....What you describe is symptomatic of a very high CC and low CC. Have you tested your water for ammonia and have you tested it with OTO and if you have what color did the OTO test turn?

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I don't know how to test for ammonia. However, that's what Ben assisted me with in the very beginning and I believe it's been gone for quite a while now. OTO testing is useless as I had needed to keep my FC at shock levels for so long now, it wasn't telling me anything useful.

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Originally Posted by JuJuBee

... reducing Alk say to add Borax to raise pH from it's 7.0 level and to keep aerating until you reach your desired pH.

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As I understand it, you lower TA by lowering pH (adding Muriatic Acid). Then you raise your pH by aerating. Repeating this process an necessary to reach your TA goal.

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...dealing with a lingering 1.0-1.5 CC. Ben had advised I raise my pH to 7.8 and keep it there as it helps get rid of the CC quicker.

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Oxidizing ammonia at a high pH produces less noxious CC than at a lower pH. This is why Ben adised you to raise your pH.

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In doing so, my Alk began to rise also. I haven't added Borax for 12 days now. My beautiful Alk is MIA...

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Adding Borax to raise pH will also raise TA. Raising pH by areating (CO2 outgassing) does not raise TA.

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...we finally hit .5 CC on June 3rd. I still have to check it this morn to see if it lasted longer than 24 hours.

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Keep at it until you have less than 1 ppm FC loss overnight and less than 0.5ppm CC plus one more day to be sure. Then your Ammonia will be gone and you can let the FC drift down. At that point you can resume your TA reduction by adding acid and aerating.

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Originally Posted by BigDave

As I understand it, you lower TA by lowering pH (adding Muriatic Acid). Then you raise your pH by aerating. Repeating this process an necessary to reach your TA goal.

Oxidizing ammonia at a high pH produces less noxious CC than at a lower pH. This is why Ben adised you to raise your pH.

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oops, got mixed up. Lots of different things going on and I haven't visited this since Memorial Day - my memory is slow to get back to where I was.

Yes, aerating was to let pH rise on it's own without raising Alk. But it wasn't rising beyond 7.2 so we had to add Borax to get it to 7.8 and keep it there - it kept falling. We haven't added Borax since May 25th, but my efforts to reach and maintain 7.8 were:

Date ------- pH ------- added
5/23 ------- 7.2 ------- 7p - 25.5 oz Borax

5/24 ------- 7.6 ------- 7a
5/24 ------- 7.6 ------- 11:30a
5/24 ------- 7.5 ------- 10p - 1 box Borax

5/25 ------- 7.4 ------- 7:30a - 1/2 box Borax
5/25 ------- 7.6 ------- 11:30a - 1/2 box Borax
5/25 ------- 7.6 ------- 3p - 1/2 box Borax
5/25 ------- 7.6 ------- 10p - 1 box Borax

5/26 ------- 8.0 ------- 8a
5/26 ------- >8.2 ------- 1:30p
5/26 ------- >8.2 ------- 10:30p

5/27 ------- 8.0 ------- 4p

5/29-5/30 ------- Alk 250 ------- added 96oz Muratic acid

-6/1 ------- 7.7 ------- 11:30a ------- Alk / cyn-Alk ------- 225 / 193
-6/2 ------- 7.6 ------- 12:30p ------- Alk / cyn-Alk ------- 200 / 170
-6/3 ------- 7.8 ------- 9:00p --------- Alk / cyn-Alk ------- 200 / 168

TODAY
- 6/5 ------- 7.8 ------- 8:45a
- FC --------- 16.0 ppm
- CC --------- .5 ppm
- CYA -------- 80
- Alk / cyn-Alk ------- 175 / 147 --------- (7 drops changed to pink/purple)
- one more drop ----- 200 / 172 --------- (8 drops changed to bright red/pink)
- Borates ----- 65? 70? (not 50 but not 80)

Quote:

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Originally Posted by BigDave

Adding Borax to raise pH will also raise TA. Raising pH by areating (CO2 outgassing) does not raise TA.

Keep at it until you have less than 1 ppm FC loss overnight and less than 0.5ppm CC plus one more day to be sure. Then your Ammonia will be gone and you can let the FC drift down. At that point you can resume your TA reduction by adding acid and aerating.

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Luckily, my testing and maint. log verify I understood this as you have written it and was taking actions accordingly. Only my memory was backwards.

Big Dave, (or anyone...)

I turned my jets down as well as the fountain just now. With the sun out right now, should I bring it to shock level since I'm down to 16 FC in order to protect the .5CC? Or would that be a waste of bleach and I should wait to add bleach until sunset?

Thank you, Big Dave.

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Originally Posted by JuJuBee

With the sun out right now, should I bring it to shock level since I'm down to 16 FC in order to protect the .5CC? Or would that be a waste of bleach and I should wait to add bleach until sunset?

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I'm not sure what you mean by protect the 0.5ppm CC. We'd like it to go away altogether. Sunlight will help clear the CC.

Since you're not fighting algae and it seems that whatever you're oxidizing stays in the water pretty well, I guess there's no harm in letting the FC drop during the day and shocking at night so as to conserve chlorine.

Do make sure you let the chlorine dose mix well and then test at night so you can test again early in the morning and compare to determine FC loss.

Will do. Thanks for letting me know so quickly. :)

I just wasn't sure if the CC could rise again if I wasn't still at shock level, (since I've been told to keep at shock level until CC is gone or not higher than .5 for 24-48 hours...) ...made me think that CC could pop back up if you lowered your FC to quickly.....?