Ryan
New member
If you’re trying to lower total alkalinity (TA) in a pool or spa, here’s the most effective and safe method. It’s a process of small steps repeated until you hit your target, and it works without damaging your water chemistry or surfaces.
The Myth to Avoid
Some people think pouring large amounts of acid into one spot with the pump off (often called “slugging”) lowers TA without dropping pH too much. That’s false. Any acid you add will lower both TA and pH. Doing it all at once can drop your pH dangerously low and damage the surface or equipment. You don’t want acid sitting in a concentrated spot at the bottom of the pool.
The Right Way to Lower TA
1. Add acid (muriatic or dry acid) to bring your pH down to about 7.0 to 7.2. This also lowers TA at the same time.
2. Aerate the water to bring the pH back up without raising TA. This could mean running jets, using a spillover spa, fountains, water features, or just pointing return jets up to break the surface.
3. Repeat the cycle: acid to drop pH, aeration to raise it back up until your TA reaches your goal.
Don’t try to shortcut by using pH increasers. Those will spike your TA right back up because they add carbonates to the water. You’ll get stuck in a loop of lowering pH and then raising TA over and over again.
Why Aeration Works
When you lower the pH with acid, you’re converting bicarbonates into carbonic acid (basically dissolved CO₂). Aeration releases that CO₂ into the air. As it leaves, the pH naturally rises again, but the TA doesn’t go back up. That’s the key.
Think of your pool like a giant bottle of soda. Acid lowers the pH and loads it with carbonation. Aeration “shakes it up” and lets the fizz out, raising the pH without adding more alkalinity.
How to Aerate
Anything that agitates the water works:
How Much Acid to Add
Use a good test kit with an acid demand test. Start by bringing pH to 7.0, not lower, and test TA. As TA drops, you’ll need less acid to hit that same pH point, and the process will speed up.
Summary
1. Lower pH to 7.0 with acid
2. Aerate until pH rises above 7.4
3. Test TA
4. Repeat until TA is where you want it
5. Once TA is right, aerate one last time to bring pH up to the normal 7.4 to 7.6 range
This is the safest, most consistent way to bring TA down without bouncing your water chemistry all over the place. It might take a few days depending on your starting numbers and how well you aerate, but it works.
Let me know if you want a specific dose amount for your pool size or need help choosing the right acid.
The Myth to Avoid
Some people think pouring large amounts of acid into one spot with the pump off (often called “slugging”) lowers TA without dropping pH too much. That’s false. Any acid you add will lower both TA and pH. Doing it all at once can drop your pH dangerously low and damage the surface or equipment. You don’t want acid sitting in a concentrated spot at the bottom of the pool.
The Right Way to Lower TA
1. Add acid (muriatic or dry acid) to bring your pH down to about 7.0 to 7.2. This also lowers TA at the same time.
2. Aerate the water to bring the pH back up without raising TA. This could mean running jets, using a spillover spa, fountains, water features, or just pointing return jets up to break the surface.
3. Repeat the cycle: acid to drop pH, aeration to raise it back up until your TA reaches your goal.
Don’t try to shortcut by using pH increasers. Those will spike your TA right back up because they add carbonates to the water. You’ll get stuck in a loop of lowering pH and then raising TA over and over again.
Why Aeration Works
When you lower the pH with acid, you’re converting bicarbonates into carbonic acid (basically dissolved CO₂). Aeration releases that CO₂ into the air. As it leaves, the pH naturally rises again, but the TA doesn’t go back up. That’s the key.
Think of your pool like a giant bottle of soda. Acid lowers the pH and loads it with carbonation. Aeration “shakes it up” and lets the fizz out, raising the pH without adding more alkalinity.
How to Aerate
Anything that agitates the water works:
- Run spa jets or waterfalls
- Point return jets upward
- Use a fountain or aerator
- Even just heavy splashing helps
How Much Acid to Add
Use a good test kit with an acid demand test. Start by bringing pH to 7.0, not lower, and test TA. As TA drops, you’ll need less acid to hit that same pH point, and the process will speed up.
Summary
1. Lower pH to 7.0 with acid
2. Aerate until pH rises above 7.4
3. Test TA
4. Repeat until TA is where you want it
5. Once TA is right, aerate one last time to bring pH up to the normal 7.4 to 7.6 range
This is the safest, most consistent way to bring TA down without bouncing your water chemistry all over the place. It might take a few days depending on your starting numbers and how well you aerate, but it works.
Let me know if you want a specific dose amount for your pool size or need help choosing the right acid.