PH question

JohnInDayton

Active member
Apr 24, 2016
31
Dayton, Ohio
#1
Tested today at pH 7.3, FC is 10. I had added some muriatic acid to get pH to 7.5, but being a little ignorant maybe, I added 5 pounds CYA 2 days ago as well since I'm trying to get CYA up to 70 from 40. Is CYA a weak acid? No one will use pool until weekend at least because too cold still here. 2/3 CYA is dissolved. TA tested at 110 before these additions and ideally is 70-80.

Should i I not bother with anything now and see what happens in a few days. The pH presumably will slightly go down more with all CYA dissolved. Do I bother increasing pH with borax or hope for good weather and have kids hopefully aerate enough to get TA down some?

What at are the hard levels for pH where I should add something to change it immediately? Seems like more worrying than necessary on my part.
 

AimeeH

LifeTime Supporter
TFP Guide
Apr 2, 2012
1,998
Columbia SC
#2
Ph of 7.5-7.8 is ideal. I personally wouldn't stress about 7.3 but how are you testing?

Aerating will indeed bring up your PH but will not affect your TA.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
9,082
Evans, Georgia
#3
How are you testing? Which test kit? What has your pH been running up to now? When did you last check?

pH tests aren't accurate with FC over 10. Does that include @10, I'm not always sure? You could be well below 7.3 since higher chlorine usually makes the pH test read *higher* than actual. I think if you're confident in your levels I'd leave it alone. If you are not you might want to use a bit of Borax and retest.
 

JohnInDayton

Active member
Apr 24, 2016
31
Dayton, Ohio
#4
I've used the pH test in my TF100 and the kit PB gave me. Been testing every couple days. pH in7.8 range before I added acid a week ago to 7.6, although FC 12-13 then , going down now with CYA going in and FC going down, makes it hard to keep straight.

Why wouln't aerating bring down TA, do I have to lower pH even more first?
 

AimeeH

LifeTime Supporter
TFP Guide
Apr 2, 2012
1,998
Columbia SC
#5
Muratic acid will lower both TA and PH. Aerating will then bring your PH back up and not affect TA.

If you find yourself needing to lower TA, that is a process where you use MA (muratic acid) which lowers both and then aerate to bring PH back up.
 

JohnInDayton

Active member
Apr 24, 2016
31
Dayton, Ohio
#6
Muratic acid will lower both TA and PH. Aerating will then bring your PH back up and not affect TA.

If you find yourself needing to lower TA, that is a process where you use MA (muratic acid) which lowers both and then aerate to bring PH back up.
Ok, I have been confused it seems. So the muriatic acid addition actually brings down TA, and the aeration increases pH to normal? For some reason I assumed the aeration decreased the TA and increased pH both. Please confirm. Is there an easy explanation for the acid decreasing TA itself?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,327
San Dimas, CA (LA County)
#7
Ok, I have been confused it seems. So the muriatic acid addition actually brings down TA, and the aeration increases pH to normal? For some reason I assumed the aeration decreased the TA and increased pH both. Please confirm. Is there an easy explanation for the acid decreasing TA itself?
Easy? Maybe. I'll try.

When you want to raise TA, you add Baking Soda. So TA = Baking Soda. What happens when you mix baking soda and acid? It fizzes and foams and releases carbon dioxide gas. It's no longer baking soda. The alkaline part has just bubbled away. Same thing when you add acid to the pool. It reacts and the gas escapes.

You know what else releases carbon dioxide gas? Shaking a bottle of soda. Aerating your pool is exactly the same as shaking a soda. The reason you can drink a soda faster after it's been poured over ice and/or has gone flat is because.... here it comes... the pH went up so it's no longer so acidic.

If you wait long enough, the C02 will escape the surface of the pool, which is why pH climbs over time. Aerating it just accelerates the process, hence the pH rises. The alkalinity was gone as soon as the acid mixed.

A final attempt: Lowering TA goes along with lowering pH. It's like a ratchet and a bolt. You push down (acid) and then you lift the ratchet (aerate). The ratchet is the pH, it comes back up. The TA is the bolt. It stays down.