Trouble lowering TA with acid and aeration

[Cybernurse]

Ia am battling a high TA of 200. I am using the lower to 7 and aerate but I'm not really getting anywhere. I only have two return jets in my pool, it is a 27 year old pool. I have pointed the eyeball up, but there really aren't any bubbles, but it is breaking the surface of the water.

Here are results when I started this process.

FC 2
CC 2.5
pH 7.8
TA 200
CH 425
CYA less than 30
temp 90
CSI .86

i added half the recommended dose of stabilizer ( just to be cautious) slowly into the skimmer per instructions on the bottle. ( I later learned I should have done it in a sock in the skimmer), left the pump running24/7, added 3 quarts and 2 cups 8% bleach to raise chlorine to 7, and 64 ounces of 20% MA. Let that work for 24 hours. Then read everything I could find on the lower TA process. (Including the "slug" paper which debunked this method)

i started the process the next day.i spent a lot of time trying to figure out who's MA amount to use, taylor lower alkalinity chart said add three gallons, pool math said 66 ounces and pool calc said 105. Went with pool calc.
DAY 1 -9 pm
pH was still 7.8
TA was still 200
FC 5
cc .5
added 105 ounces of MA to bring PH down to seven, tested again in one hour, confirmed pH was 7 and began aerating. Tested again in 2 hours, pH still 7. Continued aerating.

DAY 2 -6 am
PH 7.8
TA 200
CYA 30 ( interesting after only 4 days but I was curious)
added 128 ounces MA, Tested In 30 minutes, pH 7.4, added 64 ounces MA , tested in one hour, pH 7.0, continued aerating.

DAY 3- 6 am
pH 7.4
TA 175
Added 64 ounces MA, pH after two hours pH 7.2 ,continued aerating with just my jets pointed up.
Spent the day trying to build a better aerator seen on a post here, it was too heavy and I worried about the weight so I did not use it, old pool, 1 1/4" threaded return, I worried it would strip the thread and it is not removable. Modified it to a lighter weight one, waiting for the glue to dry and will put it in tonight.

Day3 10pm
pH 7.4
TA 150
temp down from 90 to 84
CSI .29 ( way better)

Day 3 12:30 am (now)
pH 7.8
TA 175
It does not seem I am making much headway! The pool is crystal clear and no signs of scaling that I can see. There is a multitude of very small brown stain spots all over the pool that do not brush off or feel slimy, but I opened the pool to a massive green swamp which is what got me here in desperation and defiance when the pool store said I had to drain the whole pool. I figured I had nothing to lose trying your methods. Very happy with that. Now I am an OCD tester, looking for balanced water.

so here are my questions:
how often do I need to test and adjust the pH back down to 7?
Should I be concerned about having my pH so low over several days, assuming this is going to take several more days?
why did the TA go back up after only 2 hours from 150 to 175?
is better aeration going to make this go faster and result in a more stable TA as an end result?
how long is this going to take?
can I expect my pH and TA to stabilize when I do get there?
should I be dealing with my high CH first, then worry about TA?

Obviously I am missing something and my brain is about to burst trying to absorb and apply all the information I have learned here!
Thank you all for the wonderful site and most informative education, I still have a lot to learn!

 

[chem geek]

how often do I need to test and adjust the pH back down to 7?
why did the TA go back up after only 2 hours from 150 to 175?
is better aeration going to make this go faster and result in a more stable TA as an end result?
how long is this going to take?
can I expect my pH and TA to stabilize when I do get there?
should I be dealing with my high Ch first, then worry about TA?

Test as often as is needed when you see the pH rise so you can add acid to lower it back down. The process goes faster at lower pH so don't wait until the pH gets high, but obviously it needs to get higher than you start so that you can see the difference.

The TA probably did not go up unless your pH was up. At the same pH, the TA should be going down, not up (basically acid addition plus aeration has the TA go down keeping the pH the same). Make sure you wipe the dropper tip to prevent static electricity since that can cause the drops to squirt out causing falsely high TA readings.

Better aeration drives carbon dioxide out faster so makes the process of lowering the TA go faster (along with having a low pH during the process).

Hard to know how long it will take. It goes faster when the TA is higher and slows down as the TA gets lower, but if it slows down a lot then that means your pH will be pretty stable at that point so you can stop there (i.e. no more acid) and just aerate to get the pH back up.

After you are done, you should find the rate of pH rise to be slower and you'll be using less acid to maintain the pH, especially if you have a higher pH target (say, 7.7 instead of 7.5).

Handle CH last after you are done adjusting TA.

 

[Cybernurse]

AWESOME! Thank you so much! I put the upgraded aerator in and have lots of little bubbles now! Should I put it in the deep end or shallow end? Does it matter?
i have read so very many of your posts and thoroughly trust you, so much gratitude for your time and knowledge.

 

[Cybernurse]

DAY 4 - 7am

pH 7.4
TA 175 (no change)
FC 8
CC 0
CSI .32

 

[duraleigh]

It's a process. Lower your pH again and keep aerating.

 

[Cybernurse]

Thank you so much. Doing that now. If I understand the process correctly, I want to keep my pH at 7 for as long as possible? Or do I want it to rise some then lower again?

 

[cowboycasey]

DAY 4 - 7am

pH 7.4
TA 175 (no change)
FC 8
CC 0
CSI .32

You will get there, did the aerator you built work, can you make another one? it looks like your ph is rising, you want lots of air bubbles... your PH should be rising fast with a TA that high, when it gets to 7.5 to 7.6 drop it back to 7.. does it raise back up to 7.5 in 2 hours? 3 hours?

 

[Cybernurse]

The aerator seems to work, it creates lots of small bubbles but it did not lower the TA since I started using it which was only six hours so far. Can I make another one? You mean so I can run two at the same time? I could easily do that. The pH rose to 7.4 after six hours. It has gone as high as 7.8 without the homemade aerator, i.e. just pointing the two eyeballs up but that happened after 24 hours. Today I will check pH more often to see how high it goes. I thought I wanted to lower it to 7 again as soon as it rises? Should I let it rise to 7.6 or 7.8 before I add more acid to bring it down?
I am trying to figure out how to attach a photo using my iPad or include the link to the post here that I used to build it.still working on that.

Thanks for your help!

 

[cowboycasey]

I use IMGUR to upload photos, really easy that way you dont have to put them out there for everyone, just set the size you want at the bottom and copy the bb code and paste here

As long as your still getting circulation in the pool you can use 2 fountains.. let it go to 7.5/7.6 and take back down to 7.... the more you do it the more your TA will drop, it is a slow process.. you may have to do it over days... every pool is differant so no way to know exactly how long it will take...

 

[Cybernurse]

Terrific, thank you. pH right now is 7.4. I'll let it get to 7.6 then and make a second fountain and add it. The pump running 24/7 is killing me! I'm wondering now if it might have been cheaper to just have drained the pool and start all over! I guess I'll have to drain some anyway to get the CH down. On the up side, I am way more educated in taking care of my pool, thanks to all you guys. I've spent more time on this pool in the last month than I ever have in the last nine years combined! I'm totally sold on TFPC method !

ill go check out IMGUR.THANKS A BUNCH,

 

[chem geek]

The aeration only raises the pH with no change in TA. It is the addition of acid that lowers the TA. So you keep adding acid to keep the pH low. The lower the pH and the more the aeration the faster the process will go.

 

[Cybernurse]

Ok, so that means I want to try to keep it at 7 and not let it get higher? So when do I check TA to see when to stop adding acid? Thank for the clarification

 

[chem geek]

You have to let it get higher to know that it is no longer 7.0 (assuming 6.8 is the lowest on your test kit), but you don't have to let it get higher than 7.2 and then you add more acid.

If you keep track of the acid that you add, then you'll know how much the TA is dropping. In a 14,580 gallon pool, the TA drops by 10 ppm for every 37 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid). Or put another way, every cup of full-strength acid lowers the TA by 2.1 ppm. Of course, at some point you can verify that the TA is dropping by testing it, but can wait until it's substantially lower since the test only has an accuracy and resolution of +/- 10 ppm.

 

[Cybernurse]

Okay so see if I have this right.
i started at a TA OF 200. Target is 80. That is a drop of 120.
so, 12 x 37=444 ounce of acid to add. That is close to the Taylor test kit treatment tables for alkalinity recommendation of of 384 ounces.
Maybe I've got something wrong, I keep adding acid to get it down to 7 per pool calculator. So far, I have added a total of 478 ounces. Shouldn't I be there then? After all that acid, my TA Has only dropped 25 ppm.
sorry to be such a pest but I am perplexed.
Thanks for sticking with me, I really appreciate all your help.

 

[chem geek]

Yes something does seem wrong. Are you sure you are using full-strength and not half-strength acid? Full-strength tends to fume so you'll definitely notice it if you're using it. Also, make sure your TA drops are well-formed and not squirting out and that you are holding the bottle upright. If the drops are not well-formed, then wipe the dropper tip with a damp cloth to remove static electricity.

 

[mas985]

Have you tested your fill water TA? Given your location and the fact that you are aerating so much, you are probably adding a lot of fill water (due to evaporation) which can raise TA.

 

[Cybernurse]

Yup! Verified it 31.45 and it fumes like heck when I open it. I am also doing the clean the tip of drop reagents bottle before each test,not squeezing it out but gently squeezing and letting gravity take it, holding completely vertically to the test flask, the k2006 test kit is new end of last month and I also had a new 2005 test kit which I am double checking and getting the same readings. Most of the regent expire in 2017 but none earlier than 2016.
I have been getting the pH down to 7 which is the lowest the test will go, will start targeting 7.2 per your advise so I know it's not lower than 7 and just can't show.
Fill water is testing 150 but have not needed to add any in the last week and defiinatly not any since I started this process. I've been using the 10 drop sample to save reagents but have also tested with the 25 ml sample to confirm reading.i am beginning to know the results just based on the green color gradient after adding the R0008 alkalinity indicator!
I just can't think of anything else that may be interfering. It did rain hard ( for New Mexico) the day before I started the the process and it was 200 same as it's been.
The pool is in full sun all day since I have the solar cover off with all the additions of chemicals and testing.. Water looks great, no signs of scaling that I can see. The pump has been running pretty much 24/7 for one reason or another since I opened it June 6th.
I have deep cleaned the filter, have no auto fill feature, no fertilizer or other substances getting into the water. I did have a swamp when I opened it, cleared that up with techniques found here. I did add a mustard algae treatment brand poolife, which is sodium bromine and worried I had turned it into a bromine pool when reading posts here. I emailed the company and the rep said it definatly does not turn it into a bromine pool. After that I have added only bleach, baking soda early on cuz alkalinity was low.
I am at my wits end and getting frustrated.
Thank for all of everyone's help and any ideas, tests, or suggestions are greatly welcomed

 

[chem geek]

In full sun in New Mexico this time of year you should be evaporating 9-10" per month so about 1/3" per day so over a week that would be over 2". If you didn't see that kind of drop, then that is very strange if you don't have an auto-fill.

That rep was incorrect in saying it doesn't turn into a bromine pool. It most certainly does, but the question is for how long. That is, how long does it take for the bromine to outgas or otherwise get removed because until it does any oxidizer you add to the pool creates more bromine from the bromide. Anyway, that should have nothing to do with the TA issue.

Maybe your plaster pool is adding calcium hydroxide to the water. That would raise pH, TA, and CH so acid addition wouldn't lower TA over time in that case -- it would just bring pH and TA back to where they started. The problem is that even if this were occurring, the CH and TA should rise by the same amount in ppm. Is that what you are seeing? You should test your CH and TA over a period of a week you are adding the acid to maintain the pH. If the TA is staying the same and the amount of acid is the amount of TA reduction that equals the amount the CH rose, then it's your plaster that is the source of the problem. Is this a new pool or a recently replastered pool?

 

[JayBauman]

This is a stretch, but I'll throw it out there anyway. Based on my time living in New Mexico, I recall the soil being very alkaline and the weather being quite windy. With your cover off, could some of your alkalinity be attributed to minerals in the New Mexican sandy dirt blowing into your pool?

 

[Cybernurse]

Pool was built in 1988. We bought the house in 2002. To my knowledge, the pool has never been resurfaced. Some parts of it are pretty rough to the touch.
The CH was 800 when I opened it, but that was stagnant swamp water with loads of algae. It took me 5 days to clear it up and has been clear and clean since then.When the water was clear, the CH was 450. It has gone down a tad, to 425, I am assuming due to all the backwashing and vacuuming to waste to get rid of the algae. I added probably 4" of water, I'm pretty sure of the amount because I use the tile grout line and I have measured it, which is about 7% of the total volume. (I carefully measured the water wher I normall keep it last night to be sure about my volume and need to amend my signature, the pools volume is actually 14,680.

Last CH just prior to starting this process was also 425. Testing now, CH 450. PH has been mainly 7.6-7.8 the entire time, except of course when I started lowering to lower TA. TA started at 110 for the first week then dropped to 50, I added 12 pound of baking soda over two day and it rose from that to 130, then 150, then 200 during the second week.i have recorded all my test results, date and chemical added.
When it hit 200, the pH had risen to 8. That's when I started this process 5 days ago.
I turned off the aerator about 3 pm today ( it had been running for 14 hours) because we went swimming,water felt great, a little cool and even with a pH of 7 did not burn anyone's eyes.
Interestingly, right now, after the aeration has been off for 5 hours the pH is7.2 and the TA IS 100! I trust the test results but do not trust they will last. How could it drop 75 ppm in 8 hours?

i have been concerned about the plaster just from reading other people's post and assuming it is 27 year old plaster.
so are you recommending I continue adding acid, I had thought TA Of 100! Would be an ok goal but would rather see 80. If I do keep adding acid, I'll test CH. as you suggested.