Low ph and high TA, aeration not working

[azpooldude]

Hi. New here, having some trouble with my chemistry (low PH, high TA).

I have a 21,000 gallon pebbletec pool. I heat it, min temp is 83 but its now going over that in the daytime as it heats up here in Arizona. So temp is about 85 or 86 now during the day.

My stats are this at the moment:

Total Hardness: 1000 (The water here is exceptionally hard, by the way, out of the tap...)
Total Chlorine: 3
Free Chlorine: 3
PH: 6.8 to 7.0
TA: 110 to 120
CYA: 150

I have read here and other places that aeration is the only way to bring up PH without bringing up TA. But I've been aerating for weeks now with no results. I have a spray fountain attached to one of my returns and I'm running it all day and all night (see picture). But it's not raising the PH.

I've also tried adding borax and soda ash (different experiments) to bring up the PH, but when I do the TA goes sky-high and I have to add muriatic acid to bring it down, which then lowers the PH and I'm back where I started.

I thought I read somewhere that using borax would raise PH with the least effect on TA, and that soda ash would have more effect on TA, but honestly they both seem to spike the TA.

I've been using liquid chlorine recently instead of powdered dichlor with the thought that it might increase the PH, but then I read somewhere else that it has no effect on PH.

Any suggestions?

Thanks,
Stephen

 

[Texas Splash]

Hi Stephen and welcome! I see a couple issues with your situation:
- The sprayer you have might help to keep the water cool, but it's not generating enough aeration. You would do better by pointing it downward to really agitate the water's surface. In addition, a more pressurized nozzle or fitting to give a harder effect would be better.
- While your CH is high (as expected), it's the CYA that's hurting you. Your pool and efforts would be much better served by doing a good water exchange to lower that CYA. With a CYA that high (or perhaps higher), there's almost no way to balance the FC as noted on this chart: FC/CYA Levels to avoid algae.

Is a water exchange something you can do at this time?

 

[azpooldude]

Thanks.
I thought that might be the case about the aeration. That "fountain" was about all I could find. I also tried running my (connected) spa area's jet pump 24 hours a day and having it set to overflow into the pool so the water was constantly being exchanged with pool water, but that didn't seem to do much either, and I don't like the idea of running the jet pump all the time...

Yeah, I may have to go with replacing at least half of the water. I'm almost out of time here in Scottsdale AZ before it gets too hot to drain, but it looks like we've got a cooler cloudy weekend coming up....

 

[ajw22]

Get your CYA down with a drain and then we can discuss your water chemistry and what your targets should be.

You testing with a TF-100 or K-2006C test kit?

 

[azpooldude]

I've only been using AquaChek 551236 7-Way test strips...

 

[ajw22]

I've only been using AquaChek 551236 7-Way test strips...

Then we really don’t know what your water chemistry is. Aquacheck test strips and pool store testing is totally unreliable. Get a good test kit and an accurate water test before you begin draining.

We recommend the TF-100 Test Kits or the Taylor K-2006C. See Test Kits Compared. Getting the Speedstir Magnetic Stirrer makes testing easier and more accurate. You can probably get a TF-100 before the weekend.

I suggest you review ABCs of Pool Water Chemistry

 

[azpooldude]

OK, I got the Taylor K-2006C. I just complete my first set of measurements:

CH 1000+
FC 8.5
CC 3
ph 7.0 or less (kit won't show anything less)
TA 135
CYA - off the chart (kit only shows up to 100; extrapolating mine looks like 200, only takes 1/4" of water to cover the black dot.)

So, I think I'm going to swap out most of the water tomorrow, we've got a cloudy cool day on schedule.

 

[Rancho Cost-a-Lotta]

Try to nail down your CYA by doing a diluted test. Click THIS link and scroll down to Step 8.

Good luck!

 

[azpooldude]

Try to nail down your CYA by doing a diluted test. Click THIS link and scroll down to Step 8.

Good luck!

Thanks for that link; makes a lot of sense. Will try the diluted test tomorrow.

 

[jimbethesda]

How are you chlorinating your pool? Your CYA is high, are you using pucks? They are acidic too, so maybe that’s why your PH stays so low.

 

[azpooldude]

So I tried the diluted CYA test. Still way off the chart.

So I tried a 4x diluted test (fill pool water halfway to 7ml mark, add tap water up to 14 ml mark, mix, throw away half down to 7 ml line, add reagent). At this point it reads maybe 100, which x4 would be 400! (I doubt there's any accuracy at 4x dilution, but it just shows that CYA is super high.)

To answer the other question, yes I have predominantly used pucks, and I last changed my water about 3 years ago. I've recently switched to powdered dichlor, also tried liquid chlorine, however, and will not be relying on tabs I guess in the future....

 

[mknauss]

Powdered dichlor is worse. Essentially a one to one addition of chlorine and CYA.

 

[ajw22]

I've recently switched to powdered dichlor, however, and will not be relying on tabs I guess in the future....

Dichlor even adds more CYA then trichlor in the tabs do. Chlorine is a gas and to make it a solid it needs to be bound to something. That something is CYA in dichlor and trichlor or calcium in Calhypo.

You need to use liquid chlorine.

 

[azpooldude]

Thanks - I did not know that!

Assuming I drain most of the water (which I'm doing right now) and get the CYA way down, what should I use moving forwards? I've been told that liquid chlorine does not "last"...

 

[mknauss]

You use liquid chlorine, every day. With a CYA of 50 or 60 ppm, you will lose about 3-4 ppm FC every day. You then add that back, every day, using liquid chlorine.
Or you install a SWCG, and it will generate and add your chlorine every day. You still need to run your water chemistry tests and maintain all your parameters within recommended levels.

 

[azpooldude]

I replaced most of my water. New readings:
CH 425
PH 7.6
TA 140
TC .5
CC .5
CYA 60

Where should I go from here?

 

[mknauss]

Start adding liquid chlorine every day to keep your FC in the target level for your CYA as shown in FC/CYA Levels.

Keep your pH in the 7's.

 

[an1vrsy]

Good job what you’ve accomplished in just over a week.

Now, you’re going to have to determine your pool volume in thousands of gallons. With that in mind and your known CYA level, using pool math, you can determine how much liquid chlorine you’ll need to add every day.

You’ll get into a routine with your pool maintenance and you’ll discover it is trouble free.

 

[azpooldude]

The pool is around 21,000 gallons. When using the Pool Math app, does pebbletec qualify as "plaster"?

 

[mknauss]

When using the Pool Math app, does pebbletec qualify as "plaster"?

Yes