Some questions about my water.

[jim.thornton]

FC 8.0 -- High side of normal according to the app but I prefer it a bit high.
CC 0
TA 100 or 110 (I was distracted when counting the drops. I think 10 drops but might have been 11)
CH 7 drops - turned light purple
CH 10 drops - turned blue
CYA - 50 was the last test about 1 week ago, have put in a little water since then and only used liquid chlorine
PH 7.8

So... According to the app, I need to add almost 2 cups of 14.5% muriatic acid to lower my PH to 7.6. However, another part of the app said lower it to 7.2 and aerate to raise PH. How do I aerate?? Maybe I just just add the 2 cups of muriatic acid to get it to 7.6??

I have borax which I believe raises PH, so I could do that instead of aerate?

I think the numbers are good, but would appreciate some help.

 

[mknauss]

If you wish to lower your TA, then you lower your pH to 7.2 and aerate to raise your pH back up. The acid will have lowered the TA an pH.

But if your pH is not rising rapidly, no need to mess with the TA. Just lower your pH to 7.6

I suggest you read Pool School - ABCs of Pool Water Chemistry and consider reviewing the entire Trouble Free Pool School book.

 

[jim.thornton]

Thank you @mknauss,

I assure you I have read the links that you sent me (more than once actually).

To lower PH, I will use the Muriatic Acid (14.5%) BUT... is there a correct way to do this? I've heard that you turn the pump off and pour it into the deep end with a very thin stream to get maximum depth penetration.

Then a couple of weeks ago when I was fighting the pool water, when I went to the pool store to test my water (because I didn't have the TF 100 kit yet), they told me that adding muriatic acid when the pump is on will lower PH but when it is off it will lower TA.

That makes absolutely no sense to me. A chemical reaction is a chemical reaction regardless of a mechanical pump running? Or am I wrong?

To add the acid, do I leave the pump on or not?

 

[Dirk]

The reason their advice made no sense to you, is because it makes no sense at all!!

They're describing what I think is known in the industry as an "acid slug." Some mystical, magical way a pool guy pours in acid to control and manipulate TA and pH. It's been completely debunked (the science is here on TFP somewhere, I think), but still lives on in the minds of the ignorant. Just more "pool pro" nonsense. Worse, actually, because that method is a good way to possibly stain your pool's finish.

Pump on (most definitely), pour a pencil-sized stream (or less) directly into the pool water in the path of a return's current, using that flow of water to disperse the acid throughout your pool, while keeping it off the bottom. The slower you pour, the better. That acid will do what it's going to do to pH and TA, regardless of how you pour it in, just as you thought. Dosing as I just described will put it to work a bit sooner.

Same method for chlorine, by the way.

 

[Dirk]

Oh, by the way, regarding your CH: Purple = not done. Blue = end of test. Pool School describes an alternate method for this test, that might help if you're having trouble with the colors. I find I have to wait a bit between drops to allow the color to fully develop. Slow down towards the end, the blue takes a while to show up. Like 10, 15 seconds. That's how it works for me, anyway.

 

[mknauss]

Acid column myth

 

[jim.thornton]

Thank you both.

One last question regarding the acid... I have a grecian style pool with stairs going into the shallow end at the end of the pool. On the two angled sides on either of the stairs I have a return. There are no returns in deep end at all. So, if I pour it in the shallow end, will I not be risking that it "sits" on the floor of the shallow end before getting mixed up (thereby possibly harming the liner)? If I pour it in the deep end then there is no return but it will likely disperse before getting to the bottom? What would be best in this situation?

 

[mknauss]

Pour the acid in a pencil size stream at a return with the pump running. Even in the shallow end.

If you wish to mix it more, use your brush and make a few passes to disturb the water.

The acid is very quick to mix with water.

 

[Dirk]

Acid column myth

Shoot, the link to the acid column myth debunking, located on the page linked by Marty, no longer works...