Fluctuating PH

[David Gentile]

Hi, My current pool numbers are compiled using the Taylor2005 test kit with the addition of the R 0870 DPD powder to test Free chlorine. I am also using the Taylor salt water test kit for salt content.

Pentair IC- 40 is set at 20% output. I run the pump 12 hours per day. Salt level is 4000...Free chlorine is 12...PH is currently 7.8... Alkalinity is 80...CYA is 80...Calciun hardness is 375. The pool water is perfectly clear.

I am currently having to correct the PH every 2 to 3 days. My Target PH is 7.4... Is there anyway to keep the PH more stable for longer between adjustments. Thankyou

 

[LovelyGong]

Your TA seems pretty decent for stability. What ph is it hitting before you adjust it down? Depending on CSI values I'd probably let it go to 7.6 or 7.8 before adding MA.

 

[mknauss]

Free chlorine is 12..

pH testing is not valid with a FC over 10 ppm.

Also, your SWCG is creating 1.2 ppm FC per day. That is impressively low for August in Florida. Be careful.

 

[David Gentile]

Your TA seems pretty decent for stability. What ph is it hitting before you adjust it down? Depending on CSI values I'd probably let it go to 7.6 or 7.8 before adding MA.

I adjust when the PH hits 7.8. I have been trying to keep PH at 7.4.

 

[David Gentile]

pH testing is not valid with a FC over 10 ppm.

Also, your SWCG is creating 1.2 ppm FC per day. That is impressively low for August in Florida. Be careful.

When you say be careful... are you suggesting I should raise the SWCG output higher than 20%...

 

[Flying Tivo]

A pool usually needs between 2-4 ppm of FC daily. So either you have some testing error or you have your pool volume not correct. You can turn off your swg for a day or 2 so the FC level drops to around 6-8ppm and rechck FC and Ph.

 

[David Gentile]

I have confidence in the test numbers...The pool size is 12,000 gallon.

 

[mknauss]

I have been trying to keep PH at 7.4

That is great. It will be a challenge with a plaster pool, TA in the fill water, etc.

I would suggest letting the pH rise to 8 and lower to 7.6. You may find you use less acid.

 

[David Gentile]

That is great. It will be a challenge with a plaster pool, TA in the fill water, etc.

I would suggest letting the pH rise to 8 and lower to 7.6. You may find you use less acid.

I appreciate your help. Is it normal to have to adjust PH every 2 or 3 days?

 

[mknauss]

I do in the summer. My fill water TA is 130 ppm and I lose about 1% of pool volume to evaporation each day. So I adjust my pH from 7.8 or so to 7.4 or so every other day or three. That keeps the TA around 80.

 

[David Gentile]

I do in the summer. My fill water TA is 130 ppm and I lose about 1% of pool volume to evaporation each day. So I adjust my pH from 7.8 or so to 7.4 or so every other day or three. That keeps the TA around 80.

I just tested the TAP water alkalinity...It is 70

 

[mknauss]

I suspect your pH would stay at 7.8 for quite a while.

 

[David Gentile]

I suspect your pH would stay at 7.8 for quite a while.

It is interesting that you say that. I do not know where the PH stays because as soon as I see it go to 7.8 I adjust it back to 7.4 or 7.6...I appreciate you help, Thank you

 

[David Gentile]

My PH seems to go to 8 after 3 days. My alkalinity is 70. Would it be a good idea to lower alkalinity to 60 to lower the PH??

 

[IceShadow]

If you're not using acidic chlorinating methods (like pucks or dichlor/trichlor granules) then you can let your TA drop to 50 and it is fine. If it goes below 50, raise it back up, but going to 60 would be OK. It should fall naturally as you add acid.

My pool likes to be in the upper 7's (about 7.6, 7.8) and the TA around 60-70. I've added one gallon of acid all year so far. But I also have a vinyl liner, minimal evaporation, and low TA fill water.

 

[David Gentile]

Salt level is 3900...Free chlorine is 14....PH is 8....Alkalinity is 70 calcium hardness is 375..... The interesting thing is the Free chlorine at 14. The Pentair IC 40 is only set at 20%....

 

[IceShadow]

What's your CYA from the Taylor kit?

 

[David Gentile]

CYA 70

 

[David Gentile]

I add 16 ounce of muriatic acid every 3 days to keep PH range between 7.4 and 7.8....

 

[IceShadow]

CYA 70

OK - you can target around 5-7ppm FC at that CYA with a SWCG providing chlorine. Just don't let it go below 3ppm, but you can turn it down a little and monitor to see. It'll extend the life of the salt cell, I believe, producing less chlorine.