The PH rise while aerating is really fast.

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626red

626red

New member
Jun 18, 2022
3
West Coast Canada
Hello all, new member here. Been lurking for a few months. Great to see this helpful community, hopefully I'll be able to contribute back.
Some background.... My tub is an Arctic 2021 model with the built in SWCG and Ozone, 275 Gal/ 1041 litres. Bought new and still under warranty. Went through the new owner issues such as test strips, water balance confusion compounded by the tubs probe needing recalibration, rash, tub needing multiple purges....

Now fast forward a year I have the Taylor K-2006, a digital scale and am able to move the waters parameters precisely. The issue I'm having is that when the tub is running with the air on, people in it or not, the PH will rise from a 7.4 to 8+ in about ~15 minutes.

-4 days ago -routine Ahh-some purge (just a bit of crud) Rinse and wipe out- new fill.

- Fresh water (City - somewhat green colour) fill readings;
PH 8.0
FCL 0
CCl 0
TA 30
CH 30
Temp 67 F
Added 15 grams Dichlor
Added 92 grams Calcium
Added 120 grams Sodium Bicarb
Added 20.5 grams Sodium Bisulphate
Added 5.1 Pounds Salt (2000ppm-2500ppm recommended )
New filters.
Next morning Clear water;
PH 7.6
FCL 7.6
CCL 0
TA 70
CH 80
Salt 2260 ppm
Temp 99F
Seems all good...

Combined over the next three days;
Added 30 grams Sodium Bisulphate
Added 3 grams Dichlor
Use of 2 people 1 hour

One day later to today;

Tub reads PH high warning which happens at 8.0, So I test and its 7.8( I have to get them to come and calibrate again) but decide to drop it to 7.4 to get rid of the warning. I added 10 grams of Sodium Bisulphate turned on the jets and off again in five minutes PH at 7.4. Decided to run the jets with the air on to see the PH rise and in 10 minutes it was back to PH 8.0. I then had to add another 10 grams of Sodium Bisulphate to bring it back down.

Is there something I'm missing?? Does everyones PH rise this quickly when using the jets?? Almost every time the tub is used, acid is needed unless starting PH is 7.0-7.2.

Present test results;
PH 7.4
FCL 1.2
CCL <0.2
TA 50
Temp 98F

Cheers.
 
Thanks for the responses.
A TA of 50 has been my goal, but it is a challenge and I end up going back and forth. Would it be safe to run the TA down to 40 or 30?
It just seems like I end up sitting in high PH water when its 7.4 to start.
 
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I also have this issue - a tug of war between pH and TA. My TA will be 50 and my pH will creep up above 8. So I will add some MA. I will get the pH down to 7.5 or so but then the TA goes down to 20. So I add some baking soda, but that sends the pH back above 8. It feels like a battle that I can't win!
 
I had the TA / pH tug of war with my old spa. Wirh my new one I added 50 ppm borates as a pH buffer. New tub hasn't has an issue, and in fact the tub was slowly creeping down. I was at 7 3 this morning and ran jets with air for 20 minutes uses. The pH came up to 7 6.

I use MPS and it seems to add just a bit of acidity. I think the jets (and blower) are a nice non chemical way to balance it.
 
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contentedPilgrim said:
I had the TA / pH tug of war with my old spa. Wirh my new one I added 50 ppm borates as a pH buffer.
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Why do you need this in a spa but not a pool? My pool pH is very stable - I had a cup or two of MA about once a month. Other than that, I never need to do anything to my pool as the pH and TA are very stable.

But with the spa the pH and TA are always whipsawing around. Is that due to the aeration of the spa jets screwing around with the pH?
 
wayner said:
Why do you need this in a spa but not a pool? My pool pH is very stable - I had a cup or two of MA about once a month. Other than that, I never need to do anything to my pool as the pH and TA are very stable.

But with the spa the pH and TA are always whipsawing around. Is that due to the aeration of the spa jets screwing around with the pH?
Click to expand...

Your hot tub is not 18x36.
 

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So it's been two weeks since I started this post. Researched online and have come up with a few things I was missing. One that I have not tried is the borates route, but am keeping it in the tool kit.

The other and more important thing I have learned about the PH-TA relationship, is that until the water goes through the Acid-Aerate-Acid-Aerate cycles to lower the TA and basically run the water flat like a soda pop left open, the rebound back and forth will continue. Once its flat the PH rise is far less because the aeration is less.(something about carbonic acid being produced with aeration)
Only when my TA dropped to 40 (likely different TA# for everyone)and the tub could run for an hour with only ~.2 rise in PH was the water "flat". Now I'm slowly trying to bring the TA back to 50 with Sodium Bicarbonate to see if it corrects my initial issue and allow the TA to sit at 50. So far seems to be working.
BTW I have no clue what I'm doing and no idea if its correct.
 
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With a TA between 80 and 120, and 0 borates, I found that pH rose very fast, from 7.6 to 8+ with 2-4hrs of having the jets on. To prevent pH from rising (caused by jets aerating the water):
1) keep TA as low as possible, my tap water is below 30.
2) never add any TA increaser aka sodium bicarbonate aka baking soda
3) adjust pH to 7.2, then add 50ppm of borates (e.g. BioGuard Optimizer Plus 100% boric acid, use PoolMath for exact amount to add) to buffer aka "lock in" the pH.

Since implementing this 3-step protocol, I rarely have to add acid because my pH is very stable in the 7.2-7.6 range. When it reaches 7.6, I use the calculator to figure out how much acid I approximately need to hit ph=7.2, and add that amount.
 
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