Emily Perez
Member
Please explain the acid plus aeration method to lower total alkalinity so pH stays steady, because I’m struggling to stabilize pH and I need help with the right sequence?
Lowering TA Without Wild pH Swings
- Thread starter Emily Perez
- Start date
Harper Clark
Member
I lower TA with the acid + aeration method like this: pump on, heater off. Add a small dose of muriatic acid per the label to drop pH to 7.0–7.2. Then you aerate hard (jets/air blower, cover open) to bring pH back up to 7.6. Repeat cycles until TA hits your target (usually 80–100 ppm). Don’t raise pH with soda ash let aeration do it. Test every 30–60 minutes. I can help you with dosing if you want.
Ella Robinson
Member
lower TA with the acid + aeration method: drop pH a bit with muriatic acid per the label, then aerate hard (jets/air blower, cover open) so pH rises on its own. Repeat until TA lands where you want don’t use soda ash; let aeration do it. If you want, I can help estimate the doses.
Tanvi Yadav
New member
I usually lower TA with the acid + aeration method too. Drop the pH first with a small dose of muriatic acid, then aerate to bring the pH back up without raising TA. Just repeat slowly until the TA hits your target. It keeps the pH much steadier.
Emily Perez
Member
Thanks so much, Harper, Ella, and Tanvi! This helps a lot, I’ll definitely try the acid plus aeration method and adjust it as needed. Appreciate the guidance!
Vikram Ahmad
New member
I use the acid + aeration method too, and it really is the most stable. The trick is not rushing it drop the pH a bit with some acid, then let aeration slowly bring it back up until the TA hits the number you want.
Sean Whitaker
Member
Just throwing this out there because I fought this exact thing last fall and it drove me nuts. My fill water is stubborn, TA was sitting around 140, and every time I touched pH it felt like it snapped back overnight. One day it was 7.2, next day 7.9, rinse and repeat. Jets on my hottub were running a lot and that aeration alone was pushing pH up faster than I expected.
What worked for me was slowing the acid plus aeration process way down and being more deliberate about the order. I’d add a small dose of acid, enough to pull pH down to about 7.1, not lower, then just let the jets run with the air wide open and the cover off. No soda ash, no pH increaser. I used aquadoc pH decreaser for the acid step since it was already on hand. After a few hours the pH would climb back to 7.5 or so, but the TA would drop a little each cycle. Filter pressure stayed steady, which told me I wasn’t overdoing it.
The big change was accepting that this takes days, not hours. Once TA settled around 80, the pH stopped bouncing and skin feel was way better. I still check for pH drift mid week now because heavy use will push it, but it’s nothing like before. Anyone else notice their TA fights them harder when the jets are used a lot, or is that just my setup?
What worked for me was slowing the acid plus aeration process way down and being more deliberate about the order. I’d add a small dose of acid, enough to pull pH down to about 7.1, not lower, then just let the jets run with the air wide open and the cover off. No soda ash, no pH increaser. I used aquadoc pH decreaser for the acid step since it was already on hand. After a few hours the pH would climb back to 7.5 or so, but the TA would drop a little each cycle. Filter pressure stayed steady, which told me I wasn’t overdoing it.
The big change was accepting that this takes days, not hours. Once TA settled around 80, the pH stopped bouncing and skin feel was way better. I still check for pH drift mid week now because heavy use will push it, but it’s nothing like before. Anyone else notice their TA fights them harder when the jets are used a lot, or is that just my setup?
Amira Chan
New member
the acid plus aeration method works because acid lowers both pH and total alkalinity first, then aeration brings pH back up without raising alkalinity again, so the sequence is add acid slowly with the pump running until pH drops to around 7.0–7.2, let it circulate, then aerate hard using jets, bubblers, or returns pointed up until pH rises back to normal, repeat this cycle until alkalinity settles where you want it, and once TA is stable the pH usually stops bouncing around.
Matthew Collins
Member
This method sounds complicated at first, but once you see the why, it clicks and the pH swings finally make sense.
Here’s the clean sequence and what each step is doing:
Here’s the clean sequence and what each step is doing:
- Lower pH with acid (this is the TA-lowering step)
With the pump running and heater off, add a small dose of acid to bring pH down to about 7.0–7.2. Don’t go lower than that. Acid lowers both pH and total alkalinity at the same time. - Aerate to raise pH without raising TA
Now turn on jets, air blower, point returns up, cover open, anything that adds aeration. Aeration drives carbon dioxide out of the water, which raises pH but does NOT raise alkalinity. This is the key to avoiding wild swings. - Let pH rise naturally (no soda ash)
Let aeration bring pH back up to around 7.5–7.6. Do not add pH increaser, doing that would raise TA again and undo your progress. - Repeat the cycle slowly
Each acid + aeration cycle drops TA a little. Test after each cycle. Most people repeat this over days, not hours, until TA lands where they want it (often 70–90 for pools, sometimes a bit lower for spas).
- Acid = lowers TA + pH
- Aeration = raises pH only
- Repeating = TA steps down while pH stays stable long term
- Smaller acid doses = more control, fewer rebounds
- High jet use naturally pushes pH up faster (you’re not imagining it)
- Once TA is right, pH suddenly becomes boring, and that’s the goal
John Harrison
Member
I know Emily already said thanks, so I’ll just add something a little different that helped me when I was stuck in the same loop.
What finally made it click for me was realizing I was dropping pH too far each cycle. I used to slam it down to like 6.8 thinking I’d “speed it up,” but all that did was make the water feel aggressive and mess with my saturation index for a day or two. My plaster pool did not appreciate that. Now I only take pH down to about 7.1, sometimes 7.2, and stop there.
I run a Hayward Super Pump and I’ll angle the returns up so they ripple the surface hard. That surface agitation is enough aeration for me, I don’t even need fancy fountains. After a few hours the pH drifts back up to 7.6 on its own, and TA drops a bit each round. The key for me was patience and smaller acid doses. Big hits just made the swings feel worse.
Also worth noting, if your fill water TA is high, you’re kind of fighting a slow upstream battle. Every top off nudges it back up. Once I got mine settled around 80, the pH drift calmed way down and I stopped chasing it every other day. Now it moves, but it’s predictable instead of wild. That was the turning point for me.
What finally made it click for me was realizing I was dropping pH too far each cycle. I used to slam it down to like 6.8 thinking I’d “speed it up,” but all that did was make the water feel aggressive and mess with my saturation index for a day or two. My plaster pool did not appreciate that. Now I only take pH down to about 7.1, sometimes 7.2, and stop there.
I run a Hayward Super Pump and I’ll angle the returns up so they ripple the surface hard. That surface agitation is enough aeration for me, I don’t even need fancy fountains. After a few hours the pH drifts back up to 7.6 on its own, and TA drops a bit each round. The key for me was patience and smaller acid doses. Big hits just made the swings feel worse.
Also worth noting, if your fill water TA is high, you’re kind of fighting a slow upstream battle. Every top off nudges it back up. Once I got mine settled around 80, the pH drift calmed way down and I stopped chasing it every other day. Now it moves, but it’s predictable instead of wild. That was the turning point for me.
Robert Smith
Member
One thing I didn’t see mentioned yet, and this tripped me up for a while, is testing too soon after the acid step. When I first started doing the acid + aeration cycles I’d check TA like 20 minutes later and think nothing was happening. In reality the water hadn’t fully mixed and the CO2 off-gassing hadn’t really started yet. Now I wait at least an hour of circulation before trusting the numbers.
On my setup (old Pentair WhisperFlo pump and a pretty aggressive spa spillover) the aeration step actually pushes pH up faster than expected. If the spillover runs all afternoon the pH can climb from 7.1 back to 7.6 without me touching anything. TA still drops a little each cycle, but it’s slow and kind of sneaky. I also watch filter pressure during this because when my pressure creeps up 4-5 psi it seems like circulation drops and the pH rebound slows down.
The other weird thing I noticed is that once TA gets close to its “floor” for your pool, the drops basically stop. Mine stalled around 75 ppm and just sat there no matter how many cycles I tried. At that point the pH drift calmed down and I quit chasing it. Curious if anyone else has seen that kind of natural stopping point or if its just my water behaving strangely.
On my setup (old Pentair WhisperFlo pump and a pretty aggressive spa spillover) the aeration step actually pushes pH up faster than expected. If the spillover runs all afternoon the pH can climb from 7.1 back to 7.6 without me touching anything. TA still drops a little each cycle, but it’s slow and kind of sneaky. I also watch filter pressure during this because when my pressure creeps up 4-5 psi it seems like circulation drops and the pH rebound slows down.
The other weird thing I noticed is that once TA gets close to its “floor” for your pool, the drops basically stop. Mine stalled around 75 ppm and just sat there no matter how many cycles I tried. At that point the pH drift calmed down and I quit chasing it. Curious if anyone else has seen that kind of natural stopping point or if its just my water behaving strangely.
Megan Lawson
Member
I almost didn’t jump in because the method itself has already been explained well, but one thing that helped me stop fighting pH swings was paying attention to how much aeration the pool already has.
On my setup the returns were angled up and the spa spillover runs a lot, so the pool was basically aerating itself all day. That meant pH wanted to climb naturally even when TA was high. Once I understood that, the acid plus aeration method made a lot more sense. I’d lower pH gently to around 7.1 with the pump running, then just let the normal circulation and surface agitation bring it back up instead of forcing it with chemicals.
What surprised me was how slowly TA actually drops. Each cycle only moved it a little bit, maybe 5 or 10 ppm. I’d test again after good circulation and repeat the process the next day if needed. Trying to rush it with a big acid dose just made the water feel harsh and the pH rebound harder later.
Another thing I watch during this process is filter pressure and circulation. If the pressure is creeping up a few psi and flow slows down, the aeration step doesn’t work as efficiently and the pH rise takes longer. Once the filter is clean and water is moving well, the cycle tends to work a lot smoother.
After TA finally settled around the mid-70s in my pool, the pH drift almost disappeared. It still moves a little during heavy use, but it’s predictable now instead of bouncing all over the place.
On my setup the returns were angled up and the spa spillover runs a lot, so the pool was basically aerating itself all day. That meant pH wanted to climb naturally even when TA was high. Once I understood that, the acid plus aeration method made a lot more sense. I’d lower pH gently to around 7.1 with the pump running, then just let the normal circulation and surface agitation bring it back up instead of forcing it with chemicals.
What surprised me was how slowly TA actually drops. Each cycle only moved it a little bit, maybe 5 or 10 ppm. I’d test again after good circulation and repeat the process the next day if needed. Trying to rush it with a big acid dose just made the water feel harsh and the pH rebound harder later.
Another thing I watch during this process is filter pressure and circulation. If the pressure is creeping up a few psi and flow slows down, the aeration step doesn’t work as efficiently and the pH rise takes longer. Once the filter is clean and water is moving well, the cycle tends to work a lot smoother.
After TA finally settled around the mid-70s in my pool, the pH drift almost disappeared. It still moves a little during heavy use, but it’s predictable now instead of bouncing all over the place.
Nathan Parker
Member
I almost skipped replying since most of the chemistry side was already covered, but something that helped me finally stop chasing this was realizing how much carbon dioxide loss is actually driving the whole process.
On my pool the pH rebound was way faster than I expected, and it turned out it wasnt just the intentional aeration. My return eyeballs were aimed a little too high and my spa spillover runs a few hours a day. That constant surface turbulence was basically degassing CO2 the whole time, which naturally pushes pH up even if you’re not trying to aerate. Once I noticed that, the acid + aeration cycle made more sense. I’d drop pH to about 7.1, let the pump circulate (Pentair SuperFlo VS here), and then just let the normal surface movement bring the pH back up. TA would fall a few ppm each round without the huge rebounds I used to see.
Another small thing that changed the game for me was watching my circulation instead of only staring at the test kit. If filter pressure creeps up 4 or 5 psi, the mixing slows down and the pH climb takes forever. Clean filter, good flow, and the cycle works the way it’s supposed to. Also noticed what Robert mentioned about a kind of “alkalinity floor.” Mine stalled around 70ish and just refused to go lower no matter how many cycles I tried.
Anyone else notice their pH drift speeds up a lot when the water temp gets higher? Mine starts acting different once the pool is pushing past 84 and it took me a while to connect those dots.
On my pool the pH rebound was way faster than I expected, and it turned out it wasnt just the intentional aeration. My return eyeballs were aimed a little too high and my spa spillover runs a few hours a day. That constant surface turbulence was basically degassing CO2 the whole time, which naturally pushes pH up even if you’re not trying to aerate. Once I noticed that, the acid + aeration cycle made more sense. I’d drop pH to about 7.1, let the pump circulate (Pentair SuperFlo VS here), and then just let the normal surface movement bring the pH back up. TA would fall a few ppm each round without the huge rebounds I used to see.
Another small thing that changed the game for me was watching my circulation instead of only staring at the test kit. If filter pressure creeps up 4 or 5 psi, the mixing slows down and the pH climb takes forever. Clean filter, good flow, and the cycle works the way it’s supposed to. Also noticed what Robert mentioned about a kind of “alkalinity floor.” Mine stalled around 70ish and just refused to go lower no matter how many cycles I tried.
Anyone else notice their pH drift speeds up a lot when the water temp gets higher? Mine starts acting different once the pool is pushing past 84 and it took me a while to connect those dots.