PH always rises

[alexvilper]

Hello all,

After fighting high CYA for a long, I was finally able to lower it by partial drain/refill (tried bio active, but it didn't work). Now I moving on to PH.

The problem I am having, and that I have noticed since I have owned this pool (a little over a year), is that the PH always rises, no matter what. Whether it's sunny or it rains, the PH will go from 7.2/7.3 to 8 in about a week. Every week.

Is this normal, not normal?
Is there anything that I need to be looking for in the pool itself?


These are my latest test results:

Free Chlorine 6.5
Combined Chlorine 0
PH 7.4
Total Alkalinity 50
Calcium Hardness 225
Cyanuric Acid 30


* I use DRY ACID to lower the PH


Thanks!

 

[ping]

Do you have any aeration going on in the water such as a waterfall?

What do you use for chlorine?

What surface type of pool do you have?

What is the pH of the fill water?

You already have a low TA value so that should not be the source leading to the pH rising so fast.

 

[alexvilper]

Hi ping,

No aeration.

I use liquid chlorine 12.5% from Leslie's most of the time (when it's not on sale, I use regular bleach).

I believe it's just plaster (see pic below).

I haven't tested my tap water (I will test it tonight, just to be sure), but I have not refilled it since the problem with the CYA, which is a couple of months back. We have been getting a lot of rain here.

 

[ping]

It sounds like it could be all the rain causing the pH to rise and the TA to lower. I would bump up the TA as it is getting a little too low for your pool if you don't have borates.

 

[alexvilper]

I will dump some baking soda to get it up. I'm not sure about the rain. I will keep an eye on it, though. I think it's always risen, even before the rain season. But I will watch it closely now as the rain season is about to end here in Florida.

Thanks!

 

[duraleigh]

Virtually all pools experience rising pH. Some are predictable and can be slowed.....others seem to have a mind of their own.

Wish I could offer a suggestion but it's something that cannot be overlooked. Your pH needs to stay in the seven's to comply with the things we teach.

You are doing a good job of keeping it there so it's important to stay the course. Your low TA should have slowed it down some....did you let it get there on purpose or did it seek it's own level?

 

[alexvilper]

The TA sought it's own level ;-)

It was about 80 from my last drain/refill for the CYA deal. I have been trying to keep it at 60/70 but this week it seems to have dropped a lot more. We have gotten a lot (a LOT) of rain here in South Florida, maybe that did it. After work I will put enough baking soda to go to 80 (Pool Math suggests 70-90+), and I will test it again the next couple of days to see if it stabilizes.

It does seem that I have been losing about 10ppm a week for the past 2 weeks on the TA:

09/27 - 70
10/04 - 60
10/10 - 50

During that first period, I added couple chlorine pucks to raise my CYA to the 30's because it had dropped to the 20's (ahh the irony LOL). Could that have an impact on lowering the TA? In any case, I am only using the pucks because I have a bunch of them from before I found TFP, and only when I need to raise CYA. Once pucks are gone, there will be no more

Thanks!

 

[PieMan]

I'm in Coral Springs, just down the road from you and have been experiencing the same exact thing so the good news is your not alone. The bad news is I don't have a solution either. I end up having to add about a cup of MA every few days. I do not have any aeration, added borates, and have seen my TA go from 80 down to about 40 where it is now thinking a lowering TA might keep the PH from the never ending rise and it hasn't. I thought it might be the rain but even when we go a week without rain (I know this has only happened once or twice) it still seems to rise.

 

[chem geek]

During that first period, I added couple chlorine pucks to raise my CYA to the 30's because it had dropped to the 20's (ahh the irony LOL). Could that have an impact on lowering the TA? In any case, I am only using the pucks because I have a bunch of them from before I found TFP, and only when I need to raise CYA. Once pucks are gone, there will be no more

Trichlor pucks are net acidic so yes they lower the TA. For every 10 ppm FC added by Trichlor, it also increases CYA by 6 ppm and lowers TA by 7 ppm (after chlorine usage/consumption).

 

[JoyfulNoise]

In all the posts, no one has seemed to ask the obvious question - why are you targeting such an incredibly LOW pH value (7.2/7.3)???

If I put your numbers into PoolMath with a pH of 7.2, you get a CSI of ~ -0.7. That is way too low for a plaster pool. Also, at a pH of 7.2, you have approximately twice as much dissolved CO2 (from the equilibrium reaction of bicarbonate/aqueous CO2) than you do a 7.6. Therefore, your pool water has a much greater driving force to outgas CO2 and the pH to rise (you can read all about the advanced carbonate chemistry on TFP). So your targeting of a lower pH is only making your pH rise worse. Worse yet, you are consuming TA with heavy acid use and you will eventually will have to add that back with baking soda. Pool owners fall into this trap all the time where they try to target an unnaturally low pH, consume too much TA, add it back, get rising pH and then start the cycle all over again.

You'd be way better off targeting a pH of no lower than 7.6 and then only adding acid once your pH climbs to 7.8/7.9. With your other water parameter, you are not in any danger whatsoever of calcium scaling so you can afford to let your pH ride higher. This should also cut down on your acid use which is a major plus considering your are using dry acid (sodium bisulfite) which is not really recommended because of the sulfate build-up it causes.

 

[alexvilper]

Guys, thanks for all the good info here.

@JoyfulNoise, brilliant! I don't know where I got that from, but I will certainly stop doing that. Yeah, I guess I takes a while for some things to sink in, I didn't even know about CSI, and I use PoolMath all the time, I guess I never paid to much attention to the parts below the CYA section. Thanks much!