TA creepin up fast, how to aerate?

[nitz369]

I have tested my water every 3-4 days with the TF-100. What I have found is my pH goes from 7.5 to 8.2 within a couple of days and my TA is going up 10 every 2-3 days. My TA is now at 150.

Will this number consistently go up?
Will it go down on its own?

I am not understanding how to aerate the pool if I bring the pH down to 7.0 to 7.2. None of my jets if pointed up shoot water up to get bubbles. If I use compressed air, how much do I need? I don;t have an air compresser and would assume a car of compressed air for the computer wouldn't even come close.

Should I be worried?

 

[piku]

I don't know that you have it right. Acid reduces ph and TA. Borax increases ph and (and TA I believe) but not as much as baking soda which is used primarily to increase TA. If you have constantly rising ph and TA, you would want to combat this with muriatic acid which would reduce your ph and ta. I got mine at lowes. Be careful with it, don't breathe the fumes.

Aeration would specifically be used to raise the ph without raising the TA. I've found that you need a lot of aeration to make this happen (in my case anyway).

 

[sevver]

I have tested my water every 3-4 days with the TF-100. What I have found is my pH goes from 7.5 to 8.2 within a couple of days and my TA is going up 10 every 2-3 days. My TA is now at 150.

Will this number consistently go up?
Will it go down on its own?

I am not understanding how to aerate the pool if I bring the pH down to 7.0 to 7.2. None of my jets if pointed up shoot water up to get bubbles. If I use compressed air, how much do I need? I don;t have an air compresser and would assume a car of compressed air for the computer wouldn't even come close.

Should I be worried?

I rigged up my air compressor into my return jet and ran it solid for three days and it dropped it about 100 or so. My compressor got quite a workout, I doubt it is designed to run like that either though. But I did still have to keep an eye on the Ph, because it needed constant adjustment.

 

[nitz369]

I don't know that you have it right. Acid reduces ph and TA. Borax increases ph and (and TA I believe) but not as much as baking soda which is used primarily to increase TA. If you have constantly rising ph and TA, you would want to combat this with muriatic acid which would reduce your ph and ta. I got mine at lowes. Be careful with it, don't breathe the fumes.

Aeration would specifically be used to raise the ph without raising the TA. I've found that you need a lot of aeration to make this happen (in my case anyway).

Well I understand about acid, but I think I am now understading TA, I just added acid to the pool if I test a little later the pH AND TA should be lower right?

I thought acid just reduced pH and the TA was just going up constantly.

 

[sevver]

Yes, but it isn't permanently lowered (the TA). You will need to keep you PH low, and aerate the pool somehow. Either by introducing Oxygen into the water with a compressor, or rigging some type of fountain onto a return, somehow you need to agitate the water. I have also thought of using a puddle pump, put it in a five gallon bucket in the pool (so that there is no chance of it sucking the liner, and putting a rigid pipe like pvc on it with an increaser on it capped off with a bunch of holes drilled in it as a makeshift fountain.

 

[chem geek]

I have tested my water every 3-4 days with the TF-100. What I have found is my pH goes from 7.5 to 8.2 within a couple of days and my TA is going up 10 every 2-3 days. My TA is now at 150.

Will this number consistently go up?
Will it go down on its own?

I am not understanding how to aerate the pool if I bring the pH down to 7.0 to 7.2. None of my jets if pointed up shoot water up to get bubbles. If I use compressed air, how much do I need? I don;t have an air compresser and would assume a car of compressed air for the computer wouldn't even come close.

Should I be worried?

Do you have any water aeration features such as waterfalls, spillovers, fountains or aeration jets? It is unusual to find the pH rising so quickly without such aeration and your pool isn't a saltwater chlorine generator (SWG) pool which has aeration from the hydrogen gas bubbles. By any chance, do you have an ozonator?

Your higher TA of 150 would lead to a faster pH rise, but going from 7.5 to 8.2 in just a couple of days is quite fast. Though lowering the TA via adding acid while keeping the pH low and aerating will help, I believe that other sources of aeration are the root of the problem.

As for the relationship between pH and TA, a pure acid or base will move these together, where one goes from a pH of 7.5 to 8.0 with a TA from 100 to 106, for example. Or one goes from a pH of 7.5 to 7.0 with a TA from 100 to 88. Aeration causes carbon dioxide to outgas and that has the pH rise with no change in TA.

This post shows the TA lowering procedure and how pH and TA move with acid and aeration.

Richard

 

[JasonLion]

nitz369, I suspect you have a new plaster pool? During the first three or four weeks after the plaster is applied the PH, TA, and CH levels will go up rapidly (as the plaster cures). After that it slows down dramatically, but some increase will continue for up to a year.

 

[nitz369]

nitz369, I suspect you have a new plaster pool? During the first three or four weeks after the plaster is applied the PH, TA, and CH levels will go up rapidly (as the plaster cures). After that it slows down dramatically, but some increase will continue for up to a year.

Nope Pool is 4 years old, I just bought the house, but it is plaster.

Now about the fast rise in pH, There are a couple of things that might be contributing. First thing is I figured out today that I bought 14% muriatic acid from Lowes (never doing that again) the other day, when I added the right amount a few days ago I tested afterwards and it looked like 7.5 to me (sometimes I have a hard time with reading the colors) But it probably wasn't. The second thing is there is one jet towards the shallow end thepushes water up onto the top part of the pool which is just like 4 inches deep. I think it does that to circulate that water, BUT I think it might be creating some air bubbles. I will turn that down a little more.

I will post more info when I test again.

 

[nitz369]

Okay I tested today again and pH was at 8.2.

So I officially tested 6 days ago and it was 8.2, brought down to 7.5, tested again 2 days later and it was 7.7, today it is 8.2. Does this seem right? My TA is at 160 today as well.

FC 1.5
CC 0
TC 1.5
pH 8.2
TA 160
CYA 50

Just seems like pH is going up too fast.

 

[JasonLion]

What chemicals do you regularly add to the pool?

 

[nitz369]

What chemicals do you regularly add to the pool?

I add acid and Bleach.

I just switched to Bleach about 2 weeks ago, before that was trichlor pucks and bags of "shock"

I actually still have 5 bags of "shock" left, hehe.

 

[JasonLion]

I didn't see a CH level in your water test numbers. Do you know what your CH level was before and what it is now? If CH started very low it is possible for plaster erosion/pitting to cause a PH and TA increase.

 

[nitz369]

I tested CH when I first got the kit and it was 470, I tested today and it was 500 I think, it gets really hard to tell because the water becomes so diluted its Dang near clear.

I think this is high, I bought a bottle of some Scale and hardness reducer at the pool store awhile ago and it lowered the Total Hardness down quite a bit, the Pool store says hardness will always be high in Las Vegas and you don;t need to lower it.

 

[JasonLion]

Yes, 470-500 is fairly high. In arid climates you often need to learn to live with fairly high CH levels. To manage high CH it is important to carefully keep PH from going too high, ie keep PH below 8.0. Lowering TA can also help.

Chem Geek - would scaling change the TA and/or PH?

 

[Guest]

With a TA of around 160 and an unstabilized chlorine source (bleach) your pH will rise fairly fast up to about 8.2, as you have seen. Bring you TA way down to about 60-80 ppm and you will find that your pH becomes much more stable.
Once you have achieved that you might get even better pH stability by adding borates to your pool in a 50 ppm concentration.

Also, when you lower the pH bring it ot 7.6 and not lower and add acid when it hits 7.8 to lower it back to 7.6 and not lower. This will help slow the outgassing of CO2, which is what is causing your pH rise.

With your higher calcium level your water will be less likely to scale if you bring the TA down like I suggested. If your water balance still leans toward scaling then you can also lower the pH a bit but realize that you will get a faster pH rise that way.

 

[nitz369]

With a TA of around 160 and an unstabilized chlorine source (bleach) your pH will rise fairly fast up to about 8.2, as you have seen. Bring you TA way down to about 60-80 ppm and you will find that your pH becomes much more stable.
Once you have achieved that you might get even better pH stability by adding borates to your pool in a 50 ppm concentration.

Also, when you lower the pH bring it ot 7.6 and not lower and add acid when it hits 7.8 to lower it back to 7.6 and not lower. This will help slow the outgassing of CO2, which is what is causing your pH rise.

With your higher calcium level your water will be less likely to scale if you bring the TA down like I suggested. If your water balance still leans toward scaling then you can also lower the pH a bit but realize that you will get a faster pH rise that way.

I thought I would need to lower TA, but I have been reading and it seems that it will take weeks of aeration to get it down, is this right? I also need to go rig something to actually do the aeration, my question about this process is am I able to use the pool during this process?

So I have been going down to 7.5, then I catch it at 8.2, so I need to be more diligent I guess.

 

[chem geek]

Having the pH rise, adding acid, and finding the TA slowly dropping is a "pay me now or pay me later" sort of situation. The process will occur so long as there is exposure of water to the air and the water is over-carbonated (which it intentionally is in pools to provide a pH buffer and to protect plaster). The TA is (partially) a measure of that over-carbonation.

You can either live with the situation which will very slowly over time improve as the TA drops or you can accelerate the situation towards a solution by lowering the pH and doing more aeration along with acid addition to make the TA drop faster. It does not have to take weeks and instead can take a matter of a few days if you lower the pH enough (but not below the next to lowest reading on the pH kit, so usually 7.0 or 7.2 is the lowest you go) and you aerate like crazy (an air compressor producing tiny bubbles from the bottom of the deep end of the pool provides a lot of aeration). You will need to add acid frequently as the pH rises, however, in order to keep the pH low and maximize the rate of outgassing.

What waterbear describes by bouncing between 7.6 and 7.8 will be slower, but a more regular process of getting the TA lower over time. If you drop the pH substantially to, say, 7.2, then the outgassing of carbon dioxide will be faster and the pH will rise more quickly so you'd need to add acid more frequently, but the TA will end up dropping faster. The rate of outgassing as a function of pH and TA is shown in this table.

Just turning up the returns and having the pump on high helps with aeration. Adding a fountain or shower also helps. Attaching an aeration device to a return helps a lot (search for "venturi tee" or perhaps someone has a brand they can recommend). Again, it's your choice what to do -- low pH and lots of aeration with frequent acid addition to have short-term pain, but better long-term situation OR keep the pH higher and minimize aeration to make the rate of pH rise slower.

Richard

 

[Guest]

No, I said that AFTER you get the TA down by adding a lot of acid and aerating then you will have better pH stability in the long term by keeping the pH between 7.6 and 7.8 .

To lower TA you add acid. To bring the pH back up after adding the acid WITHOUT making the TA rise again you aerate. It's really not rocket science! )

The trick is it takes a LOT of acid to lower TA and that usually causes the pH to drop lower than is desirable (below 6.8 ) so it's best to drop the pH to 7.0, which lowers the TA somewhat then aerate to bring the pH back up and repeat this process until the TA is where you want it. Once it's there it tends to stay fairly stable. You might have to bump it up slightly once in a while unless your fill water has a very high TA in which case you will have to add some acid when you top off the pool.

 

[chem geek]

Sorry waterbear, I misunderstood.

If I put in numbers for the nitz639 pool of pH 8.2, TA 160, CYA 50, CH 470 (from another post), then the saturation index is +1.0 so at very high risk of scaling so getting the pH lower is wise.

To lower your pH in your 12,000 gallon pool (from another post) from 8.2 to 7.2, it will take 69 fluid ounces (a little more than 8-1/2 cups) of Muriatic Acid (31.45% Hydrochloric acid). This will also lower the TA from 160 to about 140. It will take another cumulative 207 fluid ounces (about 26 cups) of Muriatic Acid which obviously is not added all at once, but over time as aeration makes the pH rise and you add acid to lower it. For example, if the TA is at 140, then if through aeration the pH rises to 7.6 it takes a little over 4 cups of acid to lower it back to 7.2. You'll keep aerating and adding acid and as the TA gets lower it will take less acid to lower the pH by the same amount. For example, when your TA gets to gets to 70, it will only take 2-1/2 cups of acid to lower the pH from 7.6 to 7.2. I'm just using 7.6 to 7.2 as an example -- you can certainly add acid sooner to go from 7.4 to 7.2 or from 7.2 to 7.0 if your pH test reads down to 6.8.

When you reach your TA target, just stop adding acid but keep aerating and the pH will rise at which point you can stop aerating near a pH of 7.4 - 7.6 or so (it doesn't matter that much since it will keep rising over time, but hopefully much more slowly than you are now experiencing).

I'm just giving you the above information as a ballpark so you have a rough idea of what to expect.

With your somewhat high CH you might consider lowering the TA all the way down to 60 and when you achieve that then target your pH slightly higher as waterbear suggests to the 7.6 to 7.8 range as that will reduce the rate of pH rise.

Richard

 

[Guest]

Richard,
No problem. I guess I didn't make myself clear in the first post.
What you just said above is exactly what I had in mind!