How To Lower Alkalinity In Your Pool (2 Proven Methods)


by Rick Patterson

Total alkalinity keeps your pool water’s pH level in check by absorbing fluctuations in the water balance. In other words, it’s a pH buffer.

The ideal range for alkalinity in your swimming pool is between 80 and 120 parts per million, and anything above that will ultimately lead to issues with your water chemistry.

Let’s talk about why this happens, why it matters, and how to lower alkalinity in your pool the correct way.

Why You Have High Alkalinity

Much like all great duos, Batman and Robin, Bert and Ernie, and to a lesser extent John and Yoko, total alkalinity is forever tied to the pH level of the water. 

When the pH goes up, it enters into alkaline territory on the pH scale. This rise will gradually increase the total alkalinity level as well. There’s a few reasons why this occurs.

When swimmers enter the pool, they bring with them their own pollutants that affect the water chemistry. These can be anything from natural body oils, to sunscreen or lotions they may have applied to their skin.

The water that is being used to refill the pool can also be a culprit. If it’s high-alkaline water to begin with, you can bet it will affect the pool’s total alkalinity.

Another cause for high alkalinity can be when you shock the pool. While this is performed to quickly rid the pool of pollutants, chlorine-based pool shock is highly alkaline, and can raise the water’s total alkalinity level in the process.

Why High Alkalinity Is Bad News

Nature loves balance, and your pool water is no different, requiring you to keep it in a neutral state. Once the alkalinity peaks too high, the following problems can occur:

  • It will irritate swimmers. The unbalanced nature of highly alkaline water makes it into an irritant for humans to swim in. Burning eyes and itchy skin are signs of high alkalinity, and it will also prematurely degrade bathing suit fabrics and goggles. 
  • It will reduce the effectiveness of chlorine. The high alkalinity level affects the water chemistry, and causes the pool’s chlorine to become less effective as a sanitizing agent.
  • It will create cloudy pool water. Cloudy pool water is also a sign of a pool with high alkalinity. This is because of high calcium levels that become present in the water.
  • The pH level will be too high. If your water’s pH level is high, it’s almost certain that the total alkalinity will also be high. Lowering the pH level isn’t impossible to do, but it can be a cumbersome process.
  • Scaling can occur. Due to the influx of calcium in high alkalinity water, it can cause issues with scaling throughout the pool. This will not only be evident from calcium deposits accumulating on the surface of the pool, but it can also damage your pool equipment when the water goes through your filtration system.

How To Lower Alkalinity In A Pool

Lowering the pool’s alkalinity can be done a few different ways. 

It’s important to note that you should be testing your pool water before and after you employ these methods, as you want to monitor the chemical levels at all times.

Method #1: Use Muriatic Acid

Muriatic acid (hydrochloric acid) is the most common way to lower your pool’s total alkalinity level. With a pH level of between 1 and 2, it’s inexpensive and strong enough to kill mold, remove rust, and rid the pool of calcium deposits.

While it’s the preferred method and pre-diluted, muriatic acid is also highly volatile and should be treated as such. You should make sure you’re well-protected when using it, as exposure can cause severe distress.

Be sure to deck yourself out in long sleeved attire, goggles, a chemical mask for acidic fumes, and chemically-resistant rubber gloves. As always, safety first!

Here’s how to use muriatic acid:

  1. Turn off the swimming pool pump and any water features you may have running. Muriatic acid requires still pool water to lower the total alkalinity by the widest margin possible.
  2. Use a digital test kit or test strips to determine the current level of total alkalinity in the water.
  3. Consult the directions on the bottle to determine how much muriatic acid should be added to bring the total alkalinity to between 80 and 120 ppm. Of note, it normally takes 25.6 ounces of full strength muriatic acid to lower a 10,000 gallon pool by 10 ppm. Measure properly!
  4. Further diluting the acid will make it safer. Do this by adding 1 part acid to 10 parts water (not the other way around). Use a plastic bucket and wooden stir stick to mix this solution in.
  5. Carefully pour the solution into the deep end of the pool and let it sit there for about an hour.
  6. Turn the pump back on and retest the water for alkalinity and pH.
  7. Repeat the process if necessary.

Method #2: Use Dry Acid

Dry acid (sodium bisulfate) is a granular acid that’s safer to work with than muriatic acid, but is also more expensive. You should also be careful to store it in a dry place where moisture can’t enter its container.

Here’s how to add it to your pool:

  1. Use a digital test kit or test strips to determine the current level of total alkalinity in the water.
  2. Consult the directions on the bottle to determine how much dry acid should be added, bringing the total alkalinity to between 80 and 120 ppm. 
  3. Fill a plastic bucket three-quarters full of water and add the measured amount of dry acid to it. 
  4. Mix it using a wooden stir stick until the granules are completely dissolved. Undissolved acid granules can sink to the bottom of the pool and destroy the surface.
  5. Carefully pour the dissolved solution around the perimeter of the pool, starting at the deep end. 
  6. Retest the water for alkalinity and pH.
  7. Repeat the process if necessary.

How To Bring pH Back Up

If you’ve solved your high alkalinity issue, but notice your water’s pH level is now testing too low, you can raise it with either baking soda (sodium bicarbonate) or soda ash (sodium carbonate) – but this will also raise your total alkalinity, especially the latter option.

Fortunately, there is a way you can raise your PH without affecting the alkalinity of the water, using aeration. (In fact, other than draining, this is the only way to independently raise your pH.)

Aerating infuses the water with oxygen, removing carbonic acid and raising pH in the process. This naturally occurs when the pool’s in use or when it rains, but having a dedicated aeration device (aerator) will accelerate the process.

Aerators are designed to shoot water into the air and have it land in the pool. As the water moves through the atmosphere, it picks up oxygen along the way and injects it into the pool as it lands.

There are dedicated pool aerators that can be used, but you can also add oxygen to the water through the use of pool water features like deck jets, scuppers, bubblers, and waterfalls

Finally, you can aerate using your pool’s return jets, pointing them upwards to create bubbles on the surface, or attaching a sprinkler-like product to redirect the returning water and spray it over the surface of the pool.

Pick Your Poison

High total alkalinity is a serious water issue that requires a remedy, but the good news is that there IS a remedy. 

By using either liquid muriatic acid, or a granular option like sodium bisulfate, you can gradually bring down the water’s total alkalinity to its ideal range, keeping the chemistry balanced and ensuring the pool is safe to swim in.

Categories: Pool Care, Pool Chemistry