Need help with PH and TA (long post, sorry!)

[waterbear]

are you testing the pH with the chlorine that high? If you are you are probably getting bogus pH readings. The Phenol red indicator for pH will give false high readings when the chlorine levels are above about 10 ppm (some cheapie kits it might be even lower. Pentair is one of them!) Don't test your pH until the chlorine is near normal levels and see if that helps. There have been many posts on the forum discussing this so I will not go through the chemisty of what is happening again.

[jnorris]

are you testing the pH with the chlorine that high? If you are you are probably getting bogus pH readings. The Phenol red indicator for pH will give false high readings when the chlorine levels are above about 10 ppm (some cheapie kits it might be even lower. Pentair is one of them!) Don't test your pH until the chlorine is near normal levels and see if that helps. There have been many posts on the forum discussing this so I will not go through the chemisty of what is happening again.

OK, good to know. But actually, when my FC levels have been between 5 and 10 (which is what I think it should be with a CYA of 40), PH is still bouncing some.

I think I will wait until my FC level is back below 10 before I make a decision. If my PH is still going high, with FC below 10, should I then try to raise my TA a little to see if I can stabilize my PH?

[waterbear]

I would try and adjust the pH first and see how it holds. If it is bouncing then you might want to raise the TA a bit. Vinyl pools seem to do better with a TA of 100-120 as long as your calcium isn't too high. If your water is very hard you might get some cloudiness or scaling if the TA goes too high and the pH rises. I personally would check it when the FC is on the lower side of the range....maybe 5-6 ppm. Some of the phenol red just doesn't do well with higher levels. Depends on which test kit you have. Pentair is one of the ones more prone to the interferance from what I have seen from my own experience with their phenol red.

[jnorris]

I just thought of something... the Pentair kit I am using tells me to add chlorine neutralizer (one or two drops) before I drop in 5 drops of the red stuff. Would the test still be skewed due to high chlorine?

I am also using a Walmart test kit, that test FC and PH. This one doesn't use the chlorine neutralizer. I bought this one because I was testing my FC and PH so much and didn't want to use up the DPD tablets in the Pentair kit.

I do notice I get a slightly different reading when I test the PH with both kits at the same time. I guess it is due to the chlorine.

[waterbear]

The walmart reagent is corrected for chlorine interferance better than the Pentair. It already contains some chlorine neutralizer. Adding the neutralizer to the Pentair reagent will help but do not add more than 2 drops since the neutralizer itself can cause the pH of the sample to go up.