TA and PH and FC

[jnorris]

I test using a Taylor FAS-DPD drop kit. Tested a couple of days ago, and PH was low (7.0) and TA was low (50). I figured I would adjust my PH first, since low PH is bad for a liner pool, so I added borax. Now my PH is a little too high (8.0, overshot it a little), but since I need to get my TA up some, am I OK with working on increasing the TA by adding baking soda, before I start lowering the PH? I have always been told, adjust TA first, but I just felt that the PH was a more immediate problem. I am shooting for a TA around 110-120, then when I add muriatic to bring down PH, I know TA will come down some, so maybe I'll end up around 100.

It seems like I had an easier time last year, all I had to do was add bleach and sometimes muriatic. I've not had to do much with adjusting TA before.

One more thing, I think I've read that high FC levels affect your PH readings, right? My daughter found a little speck of something green in the pool, so I have been raising my FC level (CYA is 50), to 13ppm. Should I disregard the PH reading until my FC level comes back down? At what level of FC can I reliably trust my PH reading?

 

[medvampire]

I would have used baking soda to rise my pH. The soda would have raised the ALK with the pH. What was your CC? If all you seen was a green spec in the pool I would have waited to shock untill your CC went up. FC will cause change your pH reading.
Please post a full list of your test results.
Thanks
Steve

 

[giulietta1]

An FC above 10 does interfere with the pH reading. You can add a couple of drops of thiosulfate to test the pH when FC is high, but you must keep in mind that thiosulfate is alkaline and it will bias the pH reading upwards.

It's my understanding that baking soda raises alk but has little impact on pH. . . washing soda (aka soda ash) will raise both alk & pH. Borax tends to raise pH more than it raises alk.

Once the FC is below 10, your pH test should be more accurate.

Jules

 

[jnorris]

I would have used baking soda to rise my pH. The soda would have raised the ALK with the pH. What was your CC? If all you seen was a green spec in the pool I would have waited to shock untill your CC went up. FC will cause change your pH reading.
Please post a full list of your test results.
Thanks
Steve

I used the borax, because I already had half a bag of baking soda to use for the TA, so I bought a box of borax to use for the PH. If I didn't already have the baking soda, I would have used washing soda to raise them both.

A couple of days ago:
FC 4 (I know, too low)
CC 0
TC 4
PH 7.0
TA 50
CYA 50

Yesterday:
FC 13
CC 0
TC 13
PH 8.0 (but FC was high, so maybe this reading was skewed)
TA 50
CYA 50

Today:
FC 8 (big drop from yesterday!)
CC 0
TC 8
PH 7.8 (maybe this one is reliable)
TA 80
CYA 50

I'm a little worried about the drop in FC overnight, which tells me maybe I am starting to fight something. Water is clear and clean, always had been, except a little mustard algae last year. I added more bleach today to bring it back up to 13, and will test again tomorrow to see if the level starts to hold. I guess I'll stop testing PH until I get my FC number where I want it.

 

[medvampire]

I'm a little worried about the drop in FC overnight, which tells me maybe I am starting to fight something. Water is clear and clean, always had been, except a little mustard algae last year. I added more bleach today to bring it back up to 13, and will test again tomorrow to see if the level starts to hold. I guess I'll stop testing PH until I get my FC number where I want it.

Good plan....But I would still keep an eye on the pH remembering that it may be a little off. Bring your ALK up slowly making small adjustments untill your pH holds with fewer adjustments. Think of ALK and pH being linked with a rubber band. As you raise or lower the ALK the pH will drift with it. Also if you have any water features watch your ALK for drop. Point your return eyeballs down. While making these adjustments.
Steve