New to pools and a stumper for me

[steveo]

I am new to pools (from a balancing standpoint), and new to the forums. I have read and read some more trying to figure out a few things that are going on in my pool. It is a fiberglass pool that is to my knowledge 15+ years old. The previous owners heavily neglected it. I have gotten the water back clear and removed the algae through shocking and maintaining the cholrine level properly. What I cannot figure out though is why the pH continues to rise. The TA is high in the pool and I am having a hard time getting it to lower as I only have 2 return jets and one side I just plumbed to run my polaris 360. I plan on building a homemade evaporative cooling waterfall jet. I also have jacuzzi spinners on the shallow steps, though they are old and need to be replaced. I just bought some acid to drop the pH (which continues to go up as high as 7.9-8.0 if left untreated) to begin the process of dropping the TA through aeration. Could the reason the pH continues to rise be because the TA is so high (180)? We have also had two large storms pass over (Ike and Gustav) my area and that has added alot of rain and debris. I plan on doing a shock with Bleach this weekend, but I would like to get the TA on the way down before then. My neighbor (who is responsible for getting the pool in selling condition for the previous owners) said he could not figure it out as he uses the same water source as does not have the issue. Will a high TA make pH rise?

FC = 3-5
pH > 7.6
TA = 170+
CH ~220
CYA ~ 35

 

[chem geek]

Welcome to Trouble Free Pool! Congratulations on clearing your pool of algae!

Yes, the pH is most likely rising due to the high Total Alkalinity (TA) level. You can lower the TA level by following the procedure outlined in this article in the Pool School. The key is to lower the pH to the next lowest reading on your pH test kit (7.0 or 7.2) and then aerate the water any way you can: turning returns up, running a fountain, creating an aeration jet, splashing, etc. As the pH rises, add acid to keep it low. As you do this combination of aeration with acid addition, the TA will drop.

As for where the high TA came from, it could have been from use of some sort of pH Up product or Alkalinity Up product as both increase TA levels. It can also come from a water source during refill after evaporation. Your neighbor may be using Trichlor pucks/tabs so he may also have high TA but not see the pH rise due to the acidity from the Trichlor.

Richard

 

[steveo]

Popped in a jet turned skyward, added acid in the amount of 1 gallon 4 cups as per http://www.poolcalculator.com. Also adjusted a few other balances in mild amounts. Checked this morning and pH = 7.1, TA~100, so it has dropped from the acid addition, and the pH has begun to go up, albiet very slowly.

Question: At what point to I begin to bring the pH back up and leave it? I know the TA is going to increase some when I do this. The article on lowering TA in the pool school says aeration will raise the pH. Can I assume it will eventually raise it to around a 7.8, even with the TA down at 75-80, without adding Borax?

 

[chem geek]

Once the TA level is where you want it (and gee, yours dropped pretty fast -- congratulations), you simply stop adding acid and continue to aerate which will make the pH rise with NO CHANGE in TA. The pH and TA only move together when acid or base are added to the pool. Aeration raises the pH without changing the TA. So aerate away!

In the worst case, if aeration doesn't get your pH up (partly due to the low TA, as you point out), then yes, you can add Borax to raise the pH with about half the rise in TA that using pH Up would cause.

 

[steveo]

Checked at 6PM. TA was down to 90. pH had climbed to 7.4. I dropped the pH down to about 6.9 and left the aeration going. Maybe be tomorrow my TA will be stable and my pH will be on the way back up.