Aeration - When to use it when balancing pH and TA?

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M

michy

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Sep 26, 2009
19
Hi,

My pH is stuck at 7.8 and my TA is 90. I've read Nitro's guide to lowering TA without affecting pH but it confuses me. I know I need to focus on getting my TA lower with dry acid. Say around 60, to get my pH right and stable. What I am not sure of is do I add the acid and aerate (turn on jets and blower)? Acid + aeration = lower TA. acid only = lower pH. - according to what I've read on these forums. I've been using the pool calculator and adding little bits of acid at a time, but am not sure i am using aeration at the right times.

When do I aerate and when do I not? I know the water will be balanced when aeration doesn't raise my pH. But when do I aerate when adding acid in an effort to lower TA and/or pH?

Thanks,

Michy
 
I think the short answer to your question is that you want to add lots of acid to bring the pH way down (I think the guide suggests 7.0 but you could go lower if you have the ability to measure it) before you start aerating; however, I wonder why you want to even do this? A Total Alkalinity (TA) level of 90 is fine... and will eventually come down further without any action on your part.
 
Yes technically a TA of 90 is ok, but I thought pH of 7.8 to be high. So that is why I'm trying to lower TA to get the pH lower.

"A Total Alkalinity (TA) level of 90 is fine... and will eventually come down further without any action on your part."
I'm not sure I understand how this would happen on it's own. Could you explain?

Thanks,
Michy
 
michy said:
Yes technically a TA of 90 is ok, but I thought pH of 7.8 to be high. So that is why I'm trying to lower TA to get the pH lower.

"A Total Alkalinity (TA) level of 90 is fine... and will eventually come down further without any action on your part."
I'm not sure I understand how this would happen on it's own. Could you explain?

Thanks,
Michy
Click to expand...
Without knowing a bit more about your pool (how many gallons? is it plaster? do you have a SWG? is this a new pool?) it's difficult to know why your pH is stuck at 7.8. My guess is that you're not adding enough muriatic acid. Try doubling the amount you normally add. Also, I'm assuming that you are using the Pool Calculator to determine the amount. Is that right?

Through regular application of acid the Total Alkalinity will come down over time.
 
the OP has, I assume, a spa (based on the fact that this thread is in the spa and hot tub forum!)

Whether you need to lower your TA aside, the process is this: 1) you lower your pH to 7.0, (or the lowest level your test kit will measure) which also lowers your TA. 2) Then you aerate to raise the pH, and the TA will stay down. Test pH and TA and repeat steps 1 and 2 until your TA is at the level you want.
 
describe the spa/hottub....specs...etc.

Acid only lowers PH and TA. The process for lowering TA calls for aeration in order to get the PH to the ideal level. So you use the pool calc to determine how much acid to get the PH to 7.0. This also lowers the TA. Then you aerate to raise the PH back to the mid-7s, or the desired level. By repeating this process the TA eventually gets to the range you want, and the PH should be stable in the mid 7s. Try Muratic Acid instead of dry acid, btw.

Measure carefully.... no need to rush the process by lowering the PH too low.

LOL MQ you were typing same time as me :mrgreen: and saying the same thing :mrgreen: You're the :thequeen:
 
pH 7.8 isn't necessarily a bad thing, depends on your other stats. If you post a full set of results (pH, TA, CH, CYA, borates, temp) it'll be easier to tell whether you're "treating the test" or really do need to rebalance your water.
--paulr
 
I have a 370 gallon spa with jets and a blower system. I sanitize with 3 step bromine, using MPS to shock. I use dry acid because that's what came with my start-up kit and it's what I used the first time I filled my tub. This is only my second time filling the tub, so i'm still learning. I just filled the tub a few days ago and am trying to get it balanced.

Why is muriatic acid better than dry acid? I'll consider trying it this spring...
Also, what does SWG stand for and then I'll tell you if I have it.
I have never added borates. Can this be added to a bromine tub?
I have a taylor test kit, so my stats are accurate and I am using the pool calculator:

Here were my starting numbers on a new fill:
CH:30
TA: 550 (Yes it was really this high, according to the kit! We're on well water if that explains it.)
pH: 8.4 (and probably higher since kit only goes to 8.0 and strips go up to 8.4)

Results when I posted last night:
CH: 150
TA: 90
pH: 7.8

Results a few hours later, after finally deciding to aerate for 30 min after adding acid, it finally got the pH down:
CH: 150
TA: 50
pH: 7.6
Temp: 104

I'll test again tonight to see where it's at. What happens if I overshoot and pH is too low and aeration doesn't work? Add baking soda?

Thanks for all the help so far. Really appreciate it.
Michy
 
michy said:
I have a 370 gallon spa with jets and a blower system. I sanitize with 3 step bromine, using MPS to shock. I use dry acid because that's what came with my start-up kit and it's what I used the first time I filled my tub. This is only my second time filling the tub, so i'm still learning. I just filled the tub a few days ago and am trying to get it balanced.

Why is muriatic acid better than dry acid? I'll consider trying it this spring...
Also, what does SWG stand for and then I'll tell you if I have it.
I have never added borates. Can this be added to a bromine tub?
I have a taylor test kit, so my stats are accurate and I am using the pool calculator:

Here were my starting numbers on a new fill:
CH:30
TA: 550 (Yes it was really this high, according to the kit! We're on well water if that explains it.)
pH: 8.4 (and probably higher since kit only goes to 8.0 and strips go up to 8.4)

Results when I posted last night:
CH: 150
TA: 90
pH: 7.8

Results a few hours later, after finally deciding to aerate for 30 min after adding acid, it finally got the pH down:
CH: 150
TA: 50
pH: 7.6
Temp: 104

I'll test again tonight to see where it's at. What happens if I overshoot and pH is too low and aeration doesn't work? Add baking soda?

Thanks for all the help so far. Really appreciate it.
Michy
Click to expand...
Sorry, I didn't pay attention to the forum you posted in so missed the fact that you have a spa, and not a pool. Dry acid may be a more common addition to a spa than a pool, but muriatic acid, applied in small amounts is still preferred (IMO) because it doesn't add sulphur. SWG = salt water chlorine generator. Very unlikely that you have a salt water spa so please disregard. My understanding is that chlorine added to a bromine tub will be converted to bromine.

It appears you've been successful in reducing pH and TA. I believe that aeration will work if you were to overshoot the pH. Don't add baking soda (sodium bicarbonate) because that will boost the Total Alkalinity (TA) -- I don't think this is what you want, is it? I don't know if adding pH up (soda ash) is appropriate for a spa, so others will have to answer this one.
 
So I just checked my tub after running the jets and blower for 5 minutes and my pH is now back at 8.0 and my TA is 50. How can the TA be so low and the pH have risen so high? I assume this means I need to focus on lowering my pH with acid to 7.0 and the aerate to raise pH? When I add the acid, do I run the jets and blower for 30 minutes or just add the acid and wait? don't want to lower my TA even more, which acid + aeration does. 50 is pushing it, no? Please help me understand what to do?

Michy
 

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michy said:
So I just checked my tub after running the jets and blower for 5 minutes and my pH is now back at 8.0 and my TA is 50. How can the TA be so low and the pH have risen so high? I assume this means I need to focus on lowering my pH with acid to 7.0 and the aerate to raise pH? When I add the acid, do I run the jets and blower for 30 minutes or just add the acid and wait? don't want to lower my TA even more, which acid + aeration does. 50 is pushing it, no? Please help me understand what to do?
Click to expand...
Michy,

Acid is primarily used to lower pH. The fact that it also happens to lower TA a small amount shouldn't concern you at the moment. Because this is a spa/hot tub, aeration is a normal occurrence so you shouldn't have to aerate intentionally very much or very often.

The only reason to do what your describing (lowering pH to 7.0 and then aerate to bring it back up) is when you're trying to lower TA. But I think you're already done that, so you're good to go. Now, if your pH is 8.0, it can be lowered to the Recommended Level (a pH of about 7.3 - 7.7) with muriatic acid (or dry acid if that's what you have) but not so much that it requires aeration. Did I express this well enough? If not, post back... Good luck! :-D

Greg
 
Thank you Greg, I think I understand now. Yes, my TA is fine and I don't want it any lower. So if I only want to lower my pH, I will add the dry acid diluted in water to the tub and I will just let the tub circulate it without turning on the jets or air blower. Correct? How long should I wait before retesting?

And if I wanted to keep lowering my TA but keep my pH the same, I'd add acid and aerate intentionally to mix? Right? This would lower my TA and my pH but the aeration would bring my pH back up to normal levels?

Are the following statements correct?
Aerate after adding acid when you're trying to lower TA but not pH?
Do not aerate after adding acid, if you're trying to lower pH but not TA?
And then what about if you're trying to lower TA AND pH? Do you aerate to mix? Or just pour it in and let the tub circulate it?

My tub instructions say to turn on the jets/blower to mix in all of the chemicals, so maybe this is where all my confusion started. I automatically want to turn them on after adding chemicals.

Michy
 
Alk is a buffer. It will go before the pH usually. Adding MA in small doses in 1/2 hour intervals usually has a better result at lowering the pH than slugging it, which is another way of saying you added it all at once. Slugging works well when you want to reduce the alk level. I also like to dilute the MA just prior to adding it by about a 5 to 10 parts water to 1 part MA ratio with fresh water. If a spa needs a 4 oz. dose, mixing it with 28 oz. of fresh water makes it easier to add the prescribed dose in small parts.

Always wear rubber gloves and goggles. Also, only add acid to water, not water to acid! Mix it outdoors in a large, clean bucket, the larger, the better. It minimizes spills. Safe practices are the best practices.

Using bi-sulfate to lower a body of water's pH, as was stated earlier will add sulfur. This will create sulfates that will eventually reduce a sanitizer's effectiveness. MA does not have this issue.

Scott
PoolGUyNJ
 
michy said:
Thank you Greg, I think I understand now. Yes, my TA is fine and I don't want it any lower. So if I only want to lower my pH, I will add the dry acid diluted in water to the tub and I will just let the tub circulate it without turning on the jets or air blower. Correct? How long should I wait before retesting?

Can you achieve sufficient circulation without turning on the jets? If so, that's the way to go. I would doubt it would take very long to get acid (or dilution of dry acid) to mix, so my guess would be 15 minutes or so. Members with hot tubs can answer this more authoritatively.

And if I wanted to keep lowering my TA but keep my pH the same, I'd add acid and aerate intentionally to mix? Right? This would lower my TA and my pH but the aeration would bring my pH back up to normal levels?

That's right. Follow the instructions found here.

Are the following statements correct?
Aerate after adding acid when you're trying to lower TA but not pH?

Yes, follow instructions linked just above.

Do not aerate after adding acid, if you're trying to lower pH but not TA?

Right. You can use the Pool Calculator to determine exactly how much pH will be lowered for the amount of acid you add. TA is also lowered -- but very little. You can't avoid a certain amount of lowering of TA, but this shouldn't be of great concern. If you find that TA is lowered too much, you can add sodium bicarbonate (baking soda) in small quantities to increase the value of TA. Don't add too much... you don't want to find your TA value whip-sawing up and down.

And then what about if you're trying to lower TA AND pH? Do you aerate to mix? Or just pour it in and let the tub circulate it?

It's best to pursue one goal at a time. When you need to adjust TA downward just a little, do nothing; it will come down over time by itself. When you need to adjust TA downward immediately, follow the instructions linked above.

Lower pH by adding acid. The TA will come down a bit, but usually not enough to worry about.

OK. I believe I've given you guidance that makes sense from a water treatment standpoint. If there are differences I've failed to highlight because this applies to a hot tub, other members will correct them.
Click to expand...
 
What polyvue just said (more clearly than what I was just writing, so I won't bother).

Regarding the dry acid v. muriatic question: I use muriatic in my pool and dry acid in my spa. You need small volumes of acid in a spa (on the order of tablespoons rather than cupfuls) and I find that hard to manage pouring from a gallon jug of acid. It is true that the dry acid will add some sulfates to the tub, but as it is standard practice to drain and refill the spa periodically, the buildup between refills is nothing to worry about, so I think the easier handling outweighs any other consideration for a spa.
--paulr
 
To answer your question Greg, I have a brand new tub and I think it circulates the water enough without having to turn on the jets. I'm sure diluting the chemicals first is key though.

Thank you for being patient and answering all my questions. This is great information and all my questions have been answered and the answers make sense. I'll put the theory to practice and see how it all works out.
 
If you find that the pH still rises too much for your liking even with a TA of 50 ppm or 40 ppm, you can use 50 ppm Borates as an additional pH buffer for greater pH stability. You can get the borates via boric acid in products like Proteam Gentle Spa or directly buy boric acid.
 
chem geek said:
If you find that the pH still rises too much for your liking even with a TA of 50 ppm or 40 ppm, you can se 50 ppm Borates as an additional pH buffer for greater pH stability. You can get the borates via boric acid in products like Proteam Gentle Spa or directly buy boric acid.
Click to expand...


You also get the benefit of 'silky-slippery' water with Borates. Since using it, I hardly ever have to add dry acid to keep the PH from drifting beyond 7.7 and TA consistently stays within my target +/- 5.

Also, since you shock with MPS - wouldn't that also have a tendancy to lower PH without so much acid usage?
 
I think I did have to up the pH once in a while, once i got my tub going and if MPS has that affect, then that would make sense. I don't remember having to lower the pH, once I got it balanced. I'll pay more attention this time around. I understand so much more then when I first started.

I can add borates to a bromine tub? Also, where can I buy boric acid?

Michy
 

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