SLAM'd my pool, now need to aerate?

[EnglishJimbob]

I SLAM'd with a lot of bleach because CYA was 50ish. Got that done until no overnight loss of chlorine.

Then I saw that CYA had crept up to 55, time to reduce it. I dumped water and refilled - hard to say how much but maybe 1/6 pool. Now I see CYA ~43. I'm assuming that's ok, so on to the next thing.

FC 8.5 today, TA is 140, while Ph is 7.0. CYA 43. Very clear blue water.

In calculator I'm ignoring the advice to add borax, and instead focusing on lowering TA. So I read about aeration. I have a spa jets literally in the pool, so I'm going to use those.. but I'm already at 7.0 so wondering if I should aerate to increase Ph before I add acid?

From what I've read, I should see 7.0, then aerate, then add acid to 7.0, and repeat the cycle to lower TA.

I'm going to run the spa, see if it raises Ph, then start adding acid. Never done this part before - the TA last year was ~100 and ph was usually 7.6.

 

[jblizzle]

Welcome to TFP!!!

How are your generally chlorinating? The CYA would not have gone up if you did not add it ... so the 5ppm was likely just testing variation.

You definitely need to raise the pH prior to adding more acid. Aeration is one method (although slower). Run the spa jets until the pH gets up to 7.5-7.8ish and then you can add acid to lower the TA and pH. It may take a few days for the pH to rise.

What did you add that lowered the pH so much?

 

[EnglishJimbob]

Thanks Jason. All I've added since 'opening' the pool is 8.25% bleach from the local store. I messed up a few times only raising FC to ~10, and it wasn't enough. Finally read about SLAM and after keeping FC ~25 for 3 days the algae has all gone and have no overnight loss.

Overnight with spa running I'm up to 7.6, so I added some acid to bring it down to 7.0 and will continue doing this a few days to lower TA. It's slow, but easy

> so the 5ppm was likely just testing variation

BTW, I wish there were a better way to test CYA - a disappearing dot seems so imprecise. I'm using taylor FAS-DPD, and everything else is so precise to measure

 

[jblizzle]

We all wish there was a better/ more precise CYA test

 

[Pool Tool]

While doing the same aeration trick you are currently doing, your pH rise will slow as your TA comes down. So unfortunately, if slow now then it will only get slower but that is how the balance is found. Keep it up.

 

[faby3003]

High TA by itself is not necessarily problematic. The problem is that high TA causes pH to keep creeping up. If it were me, I would not intentionally aerate my pool with a TA of 140. I would just operate as normal and see where the pH wants to reside. If pH gets to 7.8, then add acid.

My pool likes to have a TA of 120-130 to keep pH stable. Although I think my auto cover contributes to this - likely less aeration than an uncovered pool.