How to Lower Alkalinity in a Pool

Reviewed by Andrada Simion, Master of Science in Chemistry

Keeping the alkalinity level in your pool balanced is an important part of maintaining your water quality. But what should you do if it’s too high? Here’s some tips on why it might be too high and how to lower it back down:

  1. It Could Be Too High Due To Adding Too Much Baking Soda
    If your pool’s alkalinity levels have gotten too low, you might have tried to raise it using baking soda. Unfortunately, if you add too much, it’ll raise the concentration past the 80-120 ppm it should be and make them too high.
  2. Foggy Water and Calcium Deposits Are Signs It’s Too High
    While you should be regularly testing your water quality to keep the levels in balance, if the pool looks murky and you see any calcium buildup along the surface, it’s probably because you have too much alkalinity.
  3. You Can Lower It By Adding An Acidic Chemical
    If your level’s too high, that means your water has been pushed farther away from the acidic end of the pH scale than it should be. Using chemicals like muriatic acid, sulfuric acid, or sodium bisulfate will bring the pH level back to the 7.2-7.4 it should be.
  4. Remember to Turn Off Your Pump
    Before adding the chemicals, turn your pump off to prevent any turbulence in the water. If the water moves too much, it’ll introduce additional oxygen, get rid of carbon dioxide, and accelerate the effect of the acidic chemicals. This could result in the levels falling too far down.
  5. If You Accidentally Lower The pH Too Much, Aerate Your Pool
    You might run into an issue where the alkalinity level is balanced but the pH is too low. Aerating your pool to bring it back up just enough to hit the 7.2-7.4 mark. Turn on your pump to create turbulence, which helps get rid of the gas. The more you do this, the faster your level will rise, so don’t let it run too long.
  6. It Can Decrease On Its Own Over Time
    Pool water naturally becomes more acidic as time goes on, so you could try waiting until it eventually balances back out. The problem with this is if the level’s high enough for algae to begin growing, you could also end up with bacteria, viruses, parasites, and other pathogens.
  7. If The Level Rose Out of Nowhere, It Could Be From Your Water Source
    It’s possible the high alkalinity level happened on its own. You should test it to be sure. If that’s the case, you may want to find a new source, otherwise you’ll constantly have to lower the level yourself.
  8. Test and Retest
    After adjusting the level, use a pool test kit to see if you were able to hit your mark. If you don’t have a kit, you can buy alkalinity strips for relatively cheap. Test the water after six hours, twenty four hours, and forty eight hours. If forty eight hours has passed and the level is still too high, you can add turbulence to the water to try to speed up the process. Just keep a close eye on the level during this part so you don’t go too far in the other direction.
  9. It Could Take Longer Than Balancing Other Levels
    Your alkalinity level might not get back down to where you need it as quickly as the pH or calcium hardness. Keep at it until you get it, and then be vigilant about testing so you don’t run into this problem again. It’s much easier to simply keep the level balanced by tweaking it slightly when needed than to shift it wildly up or down.