Low TA, High pH - How do I get them in sync?

[Dubosity]

Hi there...been a awhile and I still have a beautifully clear pool, thanks to you :-)
I'm now concerned because I'm finding it difficult to keep my pH below 8....and it seems quite susceptible to change.

The pH had been fluctuating between 7.4 and 7.8 depending on whether it rained. I added 3 lbs of baking soda (~30K gal in-ground, gunnite pool), via the skimmer, on June 19th in order to try to get the TA to raise a bit...hoping that this would help to keep the pH more stable. Of course, this also raised the pH.
On the 20th pH was >8 (deeper red than maximum 8 on the color chart) and pH was 95. I added 3/4qt of acid (walking it around the pool). The pH went down to 7.4 but the TA went right back to 80.
Yesterday, the pH was 7.8 and TA remained at 80. (It's been raining every afternoon here).
Here are my numbers for today (K2006 test kit):
FC: 5
pH: 8
TA: 80
Calc: 250
CYA:60

I feel like I can't win! Is there any way to get the TA up a bit AND keep the pH below 8? Should I even be concerned?
I've gone back and read the tips and guides off the home page and searched around for related posts in the forum, and I have to admit that, though I didn't find anything that fully clarified it for me, I was left leaning toward doing nothing. Nonetheless, I'd rather be totally clear and confident...so I figured I'd just ask outright.

Thanks (in advance) for sharing your knowledge.
Debra

[Watermom]

By any chance, are you aerating your water? (Ex. -- is your return jet pointed upwards creating bubbling on the surface?) if so, aim the jet down.

Go ahead and add some more baking soda. Baking soda shouldn't change the pH much but will increase the TA. Add a couple of lbs. at a time until you get it up to about 110 or so. After each addition, wait a few hours, retest TA and then redose with more baking soda until you get it to the target. Then, add a little muriatic acid slowly in front of the return jet. Wear gloves, glasses, pour close to the surface of the water to avoid splashing, stay upwind of fumes. Test pH a few hours later and redose with more acid until you get to about 7.4-7.6.

When you are adding the baking soda and then the muriatic acid, you do not have to wait more than a couple of hours between additions of more.

Hope this helps.

[Dubosity]

Hi,
The jets are pointing more up than down. I wouldn't say the streams completely break the surface but they come close. You can definitely see the water rippling at the surface when the pump is on.
I'll do as you say; however, the last time I did the soda/acid routine, I ended up at square one. So I think I must be doing something wrong. After adding the soda, the TA was up (a bit) but the pH skyrockted! Then when I added the acid to bring the pH back down, the TA went right back down to its starting point of 80.
I had dissolved the baking soda in a bucket of water and added that to the skimmer. Did this method cause the pH to rise so much?

And one more question: When adding the acid, should I be as far as possible from (or as close as possible to) the skimmer? Does it matter?

[Watermom]

You're using baking soda and not washing soda? Baking soda should not affect pH so much but washing soda will cause them both to rise substantially. Add the baking soda to water first would have no effect on anything but you really don't have to do that step. You can just add it slowly to the skimmer while the pump is running.

When adding acid, you do NOT add it to the skimmer. Add it in front of a return jet. If you have more than one jet, I'd say it probably doesn't matter which one you pour it in front of. I guess I'd probably go with the one that is the farthest away from the skimmer if it were me.

[Dubosity]

Hi,
Yes...baking soda, not washing soda. Any idea why the baking soda affected the pH so substantially?
Well...I'm gonna go follow your instructions. I'll keep you posted.
Thanks again!

[waterbear]

The rainwater is aerating the pool and causing the pH to rise so you do not want to RAISE the TA you want to LOWER it! I wll explain:

There is a common misunderstanding about low TA and high pH. It takes a LOT MORE ACID to lower TA than to lower pH so when you need to raise the TA with baking soda...
adjust the TA to desired range AND GIVE THE WATER A DAY TO STABILIZE BEOFRE YOU TEST THE pH. The pH will be often too high (usually ending up around 8.0) so lower it to target pH with acid and you are good to go (since the amount of acid needed to lower the pH will not have any measurable impact on the TA) but...
a few things to consider...
Higher TA levels will not 'stabilize pH', what they will do is cause pH to rise faster...Now, if you are using an acidic sanitizer source (trichlor tabs, dichlor, bromine tabs, MPS--non chlorine shock) THEN having a higher TA will help stabilize pH by offsetting the constant addition of acid that is the effect of using these products BUT...
IF you are using an unstabilized chlorine source (sodium hypochlorite--liquid chlorine or bleach, calcium hypochlorite--cal hypo, or lithium hypochlorite), which are all basically pH neutral (alkaline when added, acidic on sanitation so the net effect on the water is pH neutral) THEN you want to have a lower TA since the higher the TA the faster CO2 outgasses and the MAIN cause of pH rise in pools using unstabilized chlorine (assuming that we are not dealing with new plaster) is outgassing of CO2 so...
to minimize pH rise there are a few things you can do:

1. target a lower TA (less than 100 is good and even as low as 60 ppm if the pool has a lot of aeration. If this is a plaster pool be sure to raise the CH to maintain the saturation index)

2. Don't lower the pH too much. the lower the pH the faster it rises because the lower the pH the more we convert bicarbonate in the water (TA) to carbonic acid (carbon dioxide in the water) and the more carbon dioxide in the water the faster it will outgas which means the faster the pH rises! We use this fact to our advantage when we are lowering TA!
Keep the pH NO LOWER than 7.6 and wait until it rises above 7.8 before lowering it to 7.6 and not any lower. It will take a bit of trial and error at first (and, if you have one, an acid demand test) but soon you will know how much acid you need to add and how often to maintain this.

3. If you are at high altitiude CO2 WILL outgas faster (you really don't want me to get into the science behind this!) so the best thing is to keep the TA very low (60-80 ppm)

4. adding a secondary borate buffer system will help because it works in the opposite direction from the bicarbonate buffer we call TA and helps keep the pH right around 7.6-7.8 for a long period of time. You can use an expensive borate product lke Proteam Supreme, Bioguard Optimizer, Pool Life Endure, or Guardex Maximizer or your can use 20 Mule Team Borax and Muriatic acid at the rate of 60 oz by weight of borax and 30 oz by volume of muriatic acid for every 1000 gallons to reach 50 ppm. If you don't want to mess with the muriatic acid you can instead use boric acid at the rate of 60 oz by weight but you will have a very slight pH drop (that is normally nothing to worry about or change since it will rise on its own in time).

A final note, it makes no difference if you 'walk the acid' or not...adding acid lowers both pH and TA but it lowers pH much faster than TA so it takes a LOT MORE ACID to lower TA so when you need to add acid either SLOWLY pour it into a return stream away from the skimmer or dilute it in a bucket of pool water and broadcast it over the surface. The only reason to walk acid is if you really need the exercize! The whole thing about 'walking vs. slugging acid' is an old wives tales that rrefuses to die in this industry even though it has been disproven!

[CarlD]

Evan asks a question implicitly I would ask FIRST before taking the steps he's indicated:
Is this a concrete/shotcrete/tile/plaster pool? Is it new or newly surfaced? If so, the curing of walls is raising your pH and your efforts will be for naught--you just need to keep adding Muriatic acid.

If, however, that's not the cause of the rising pH (such as you have a vinyl pool), a lower T/A may well help. This season, for some screwy reason, my T/A has been just around 60ppm and I haven't messed with it because my pH has been locked in at 7.6 for 6 weeks without doing ANYTHING. So...why would I raise T/A? Normally I keep T/A at 80-100 but....pH hasn't moved and T/A's "job" is to keep pH stable.

So try lowering T/A to 60 or even lower and see if the pH keeps rising.

Meantime, keep Muriatic Acid around and keep adding it. For long-term use MA is better than Dry Acid as it's just Hydrochloric Acid--nothing extra goes into the water.

Good luck!

Carl

[Dubosity]

Given that I've already added 2 doses (2# each) of baking soda before I saw Evan's and Carl's posts, I guess I just now need to wait until tomorrow and test the pH and then just add MA to get the pH down to 7.6. Right? I do have an acid-demand test and feel very comfortable using the chart in the back of the Taylor book to determine the amount of MA to add.

Carl and Evan: It's a gunnite pool, older...not newly resurfaced or anything like that...and I'm about as low-altitude as you can get, living in north-central FL. Oh yes, and I'm using bleach (though I plan on going to LC from the pool supply store as it'll work out to be much cheaper).

I did read the article on maintaining a high-pH pool (a couple of times)...that's why I was inclined to do nothing...but I never got that it's also okay to keep such a low TA. I've now read and re-read your post, Evan, and I think I get it. Interesting.
It sure would be nice not to have to keep such an eagle-eye on the pH and continually adding MA, but I'm not sure I fully understand the borate option. Are you saying to add borax and MA together? Is that a one-time deal or does it need to be done regularly? Maybe I should just suck it up and keep adding the acid?

Oy :-)