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

[JuJuBee]

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.

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)

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.

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.

[JuJuBee]

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.

[BigDave]

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?

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.

[JuJuBee]

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.....?

[BigDave]

The CC is a byproduct of the FC oxidizing the (presumptively) ammonia in your pool. It's always an indication that there's something in the pool that's being oxidized by the chlorine.

The goal of shocking is to get rid of stuff in your water that doesn't belong there. When you can hold (less than 1 ppm loss) FC overnight (no loss to sunlight) and measure nearly no (0.5ppm or less) CC for two nights in a row, you'll have have finished shocking (gotten rid of unwanted pool stuff).

[PoolDoc]

Hi All;

I've seen some things that make me suspect that, with the DPD-FAS test, you will see a CC residual, when the FC gets high enough, even though there may be no actual CC's present. It's something that needs to be tested, first with distilled water at FC=50 ppm and then with distilled water + 20 ppm CYA at 50 ppm FC.