pH rise, Creeping TA, rising CH, etc.

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red-beard

red-beard

Gold Supporter
May 27, 2019
1,624
Houston, TX
Pool Size
25000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
My pH rise has been quicker than usual, so today I did a full chemistry check.:
FC 9. CC 0. pH 7.8 (I added acid to reduce to 7.6 2 days ago), TA 90, CH 425, CYA 60, SALT 2900, BOR 25, Water Temp 89, Calculated CSI 0.21

CYA is 60, lower than my normal 70-80. With water temp regularly going above 90, a reduction in CYA is not unusual. Adding 4.25 lbs CYA...I use a version of the sock method using a very fine mesh net and place it in front of my old pressure side pool cleaner wall socket with the pressure side pump turned on. CYA is already gone! It took about 1 hour! See pictures below.

TA is 90. It was 70 early in the season but is creeping up. I know this is driving the pH rise. We have not had significant rain for several months; my water additions are driving my TA up. My CA (carbonate Alkalinity is around 65, which puts my pH ceiling around 8.25. I added a gallon of MA (which lowers TA by 20) and I'm running my submersible pump as a fountain to raise pH. I think I'm going to have to do it again to get my TA way down before I up my Borates from ~25 to 50. With the CYA fixed and TA fixed, my CA should be around 38, with a pH ceiling of 8.0.

CH is 425. The real worrisome thing is my rising CH. Again, the constant water evaporation and water adds are also driving this. I'm up to 425 and it is only mid-July. I really do not want to do a drain...But with the SWG, I am always concerned about scaling. CSI is up to 0.21 with a pH of 7.8! This is why I'm attacking the TA. It looks like I may need to run a slightly lower pH to keep CSI slightly negative. If I get my TA to 70 and my keep my CYA at 80, I now need to adjust pH at 7.8. Looks like my new target pH is 7.6 when the pH gets to 7.9.

I have a feeling that a 25% drain and refill is in my future...And then I have to FIX the chemistry again....

Modified Sock method:

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Cheesey Submersible Pump Fountain

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My fill water is about TA 125ppm on average. I have not noticed a significant change in my TA - it did go to 80 but I got it back down to 70. My water softener is also connected to my tap that feeds my pool fill so I do not add any CH increase, in fact with recent rains I have seen a slight decrease in CH - from 400ppm to 350ppm on my most recent test.

Also my CYA has been holding at the 50 ppm but I have gone on several extended trips and was supplementing trichlor pucks with my LC when I was away.
 
Plug your goals into poolmath csi -
When i put in your current ch, ph of 7.8, ta of 60, current water temp, borates of 50 & cya of 70 or 80 - csi remains negative until i raise ch up to 800. Do what you are planning & don’t sweat it too much. Also as the temp lowers your ch will have risen so take that into consideration as well when the weather turns
 
Borates are 25 at the moment. Once I have the TA down, I'll add the borates, unless I decide to drain some water for CH reduction. With 50 ppm Borates, my CA would put my pH ceiling at 7.95. BTW - TA will only drop to 70 with the 1-gallon addition. Try it with a 70 TA
With the rising CH, I want to make sure my CSI is slightly negative, to prevent calcium buildup on the SWG cell. I know that Borates should also help this. Step by Step...
If my TA is 70, CYA 80, BOR 50, CH 425 and water temp 89-92 degrees, I can have a pH up to 8.0 and a CSI of 0.03. While not negative, it is nearly neutral, within testing accuracy. Seems like the TA reduction, CYA fix and Borates raise will put me in a good place.
 
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Update: My first pH reading was 6.9. At 6PM tonight, it is reading 7.0. I need to get the pump in place to drive the CO2 out of the water! I may need to dose some more MA once the pump arrives in the morning.
 
This morning, the pump arrived from Amazon at 5:50 AM! I did not install it before 7AM...It is a 1 HP pump, and it is quite a bit more powerful than the 1/3 hp pump I had operating. It is supposed to be about to pump up to 4200 GPH and the spray reaches about 30 feet down the pool! Big splash!

Readings this morning:

FC 10, CC 0, pH 7.1, TA ~75, CYA 80, Water Temp is 89 in the morning, but will reach about 91 in the late afternoon. On the TA reading, it changed color from greenish to red at 7 drops. But an 8th drop the color became darker. 9 and there is no change. This says to me the TA is somewhere between 70 and 80. Once the pH gets above 7.3, I'm going to do another MA add to drop the TA by 5 points. Pool Math says this is 1 quart or about a liter. I'll re-check the pH in a few hours.

With 75 TA, CH 425, CYA 80 and Borates 25, my CA is 42.7 which has a pH ceiling of 8.06. I definitely want this lower! So further TA adjustment!
 
wireform said:
The last drop doesn't count if it didn't change anything but your 8th droplet caused it to go darker so therefore you're 80.
Click to expand...
I know that is the "wisdom" here, but it is probably between the two drops. I'm dropping my TA by another 10 points to get into the 60-70 region. But I want my pH to rise a bit more first.
I re-ran the Ta test. I diluted the Taylor Sulfuric Acid 0.12 Agent 50% (I measured with a 1 cc syringe!) with distilled water. It came out at exactly 14 drops. Color change started at 11 drops (purple), went darker purple 12, red 13, darker red 14, no change at 15.

At 70 TA, I don't need to really drop the TA again.

I wonder if we need to drip one drop first before starting our tests!
 
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proavia said:
Everything is within range.
Don't obsess over the pH, TA and CSI.
Go for a swim.
Have another adult beverage.
Don't check the pH until late tomorrow.
Click to expand...
Said to an engineer. It is hard to swim with a pump in the pool which is working on raising pH after a TA reduction...

And as far as CSI is concerned, I do obsess. I want it slightly negative in my normal pH ranges. I do not want scaling in my SWG cell.
 
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I forgot....
Take that pump out - let the pH come up on it's own. You are wasting electricity running it and will need to add more acid sooner.
Your CSI is within acceptable range of 0.60 to -0.60. Soon enough it will be within the 0.00 to -0.30 range you desire to minimize SWG scaling - and that's when your goal will be to keep it there.
No need to force it, it will get there.
Relax and enjoy the clear fact that it's all okay.
 
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Pump removed at 8PM last night. I was following the directions at posted in theses here pages...Aerate to 7.6 pH

pH was around 7.5 this morning. I have not checked tonight. I'm going to run FC, pH and TA in the morning.
 
red-beard said:
I need to get the pump in place to drive the CO2 out of the water!
Click to expand...
That's not really how it works chemically. Stirring up the water with bubbles, jets, swimming, waterfalls, etc just speeds up the process of calcium carbonate alkalinity swapping bonds with the hydrochloric acid you added. Chemically, the result is carbonic acid, which is the same thing as "carbon dioxide dissolved in water." Honestly, hosting a pool party with cannonball contest probably creates more bubbles than your aerating rig.

It really does just happen on its own whether you aerate or not. It just happens faster with aeration, which is important to do if you've just drastically dropped the pH (and by extension the CSI) of your pool water.
 
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