Guide To Pool Alkalinity

Maybe you’re a new pool owner looking to understand the idea of pool alkalinity. Or maybe you’ve had a pool for a while but never quite grasped the concept. Whatever your situation may be, we know that balancing your pool’s chemicals can be daunting, and what better way to start than by understanding pool alkalinity?

Alkalinity stabilizes the pH balance in your pool. Keeping it in a normal range (80-120ppm) is critical to maintaining a chemical “balance” in the pool. Heavy rain or replacing lots of water can lower alkalinity out of range and cause cloudiness quickly. Adding household baking soda increases alkalinity.

So, if you’re looking to understand what alkalinity is (plus the difference between alkalinity and pH), the factors that affect it, and how to raise or lower it, you’re in the right place. Let’s get started!

What Is Pool Alkalinity?

Checking the water quality of a pool with the help of a test strip with PH value

Total alkalinity is the pool water’s ability to withstand a pH changes without losing chlorine effectiveness. Ultimately, total alkalinity limits drastic changes in the pool’s water balance.

Whenever anything that could change the pH of pool water comes into the water, total alkalinity responds by neutralizing it and maintaining the pH in the correct range. You should note, however, that total alkalinity helps keep the pH within the desired range but won’t determine the pH.

So, how do you measure total alkalinity? You can determine total alkalinity using a test kit (on Amazon) to measure it in parts per million (ppm). You should maintain it at 80-120 ppm, otherwise the water will become “unbalanced” and controlling the other chemicals, like chlorine, becomes much harder.

Additionally, with a value of more than 120 ppm, the water becomes foggy and even causes scale on things like pool ladders, skimmers, and the pump and its components.  

What’s the Difference Between Alkalinity and pH?

Contrary to popular belief, alkalinity and pH are different.

A pH reading determines how acidic or alkaline water is. The scale ranges from corrosively acidic, at a level of 1, to highly alkaline at a level of 14, with 7 indicating neutrality.

An excellent example of a neutral substance is water. Lemon juice will pass at a pH of 2 (highly acidic) and bleach comes in at 13, which is considered very alkaline.

Alkalinity and pH are distinct things, but they’re linked in that when your alkalinity is low, your pH is also low, and vice versa.

Low Alkalinity vs. High Alkalinity

Low and high alkalinity affect your pool differently. Here’s a quick overview of both alkalinity levels.

Low Alkalinity

One sure sign that you have low alkalinity is the fluctuation levels of your pH varying from too high to too low. Usually, the numbers shift drastically, forcing your pool’s pH to be unbalanced, and it can lead to the following issues:

  • Staining of the pool
  • Ineffective chlorine
  • Metal corrosion

High Alkalinity

High alkalinity clearly shows itself through cloudy pool water, indicating that your pH is higher than usual. It also causes issues such as:

  • Congested filter
  • Minimal pool circulation
  • Coarse surfaces

As a pool owner, pool alkalinity is vital to your pool water’s chemistry. But take caution not to succumb to the deception of some “pool experts” who’ll try to sell you anything for your pool’s maintenance. Apart from poor pool upkeep, some of their products may result in low alkalinity.

Factors That Affect Pool Alkalinity

The best way to deal with alkalinity issues is to first determine what affects the alkalinity of your pool. So here we go:


Because of air pollution, especially in urban areas, rain flows with sulfuric acid. If the pH of the rainwater is 5, for example, it will eventually lower the swimming pool’s pH. So, immediately after a downpour, make sure you measure the pH levels of your pool.

And note that the alkalinity of rainwater is basically 0, so whatever your alkalinity is, rainwater will reduce it. Testing alkalinity after a rainstorm and adding normal baking soda (on Amazon) to increase it can help you ride out the effects of storms on your pool’s chemistry.

Pool Structure

Yes, the pool’s structure can affect your pool’s water pH. For instance, Pebble Tee surfaces are porous and alkaline, so they can consume and neutralize acid, raising the pH of the pool water.

This is because only low acid concentrations are necessary to maintain the appropriate pH balance. On the other hand, surfaces that don’t soak in acid are vinyl, fiberglass, and colored plaster pools.

Whenever your pool’s acidity rises, during rain, for example, sodium bicarbonate or soda ash will come in handy to maintain the pH.

Citrus Plants

Due to the citric acid in citrus plants, they significantly lower the pH when they find their way into the swimming pool. Therefore, keeping citrus plants, fruits, and leaves as far away from the pool as possible will help stabilize your pool’s pH.

You should also uproot any citrus plants nearby or ensure your pool is consistently covered to manage this situation.

Soil and Dirt

Soils in dry areas tend to be alkaline and can considerably affect your pool’s pH. Remember, alkaline components neutralize acid and increase the water’s pH. So you don’t want any dirt filling your pool.

What if your location encourages a lot of dirt and debris to enter your pool? In this case, it would be best to cover your pool more often.

How to Lower Alkalinity in a Pool 

Acids are the remedy to high pH.

Lowering your pool’s alkalinity requires you to gradually add some acid (in liquid or powder form) over several days. Don’t add the acid all at once because the pH will drastically drop, corroding the pool’s surfaces.

With high alkalinity, you should use an acid such as muriatic acid (on Amazon) or sodium bisulfate (also on Amazon) to lower it. After getting your acid from any pool and spa store:

  1. Add it to your pool water until it reaches a pH of 7.
  2. Shortly after, see whether the pool returns to a pH of 7.2.
  3. Continue looking until the pool’s alkalinity stabilizes while following the acid’s directions to the latter.

How to Raise Alkalinity In A Pool

Pool has been cleaned and ready for the swimming season

You can raise a pool’s alkalinity through baking soda (sodium bicarbonate/baking soda). Use 1.5 pounds of sodium bicarbonate per 10,000 gallons of water to raise alkalinity by 10ppm. So, for example, if you measure an alkalinity of 50, and you want it to be 100, you need to raise it all by 10ppm 5 times. If the pool is 10,000gal, then that means adding 7.5lbs of baking soda.

If you’re unsure how much water you have, you can get away with eyeballing it as long as you do it on the low side: if your alkalinity is very low, add 2lbs of baking soda and see what effect that has on alkalinity. If it raises alkalinity from 60 to 80, and your goal is 100, you know you need to add 2 more lbs to get there. If it only raises it from 60 to 70, you know you need 6 more lbs to get up to 100.

When increasing total alkalinity, an alkalinity booster (on Amazon) should be in your arsenal. In this case, you should add the necessary amount reasonably over a few hours while the pool is circulating.

But remember, while many chemicals will be branded as “alkalinity booster” or “alkalinity up,” you don’t need a special pool chemical for this. As mentioned above, you can use normal, garden-variety Baking Soda (on Amazon) to do the job just fine.

Occasionally, you’ll have to correct the total alkalinity and pH, especially in a new pool. Usually, when one factor is high or low, the other is as well. But you can also encounter a situation where one element is very high, yet the other is very low. Here, altering the wrong element first will interfere with the other aspect and cause metal corrosion.

So, what should you do? Once this happens in a new pool, it would be best to wait one day before changing anything. After that, you’ll notice that the water will naturally come to equilibrium (balance) with no chemicals used. If you need to make further changes, you’ll do it in less time and with fewer chemicals.

With a low pH and high alkalinity, first elevate the pH to around 7.2 – 7.8 before lowering the total alkalinity. If the total alkalinity is low and the pH is high, first increase the total alkalinity and then lower the pH.

If the pH of the pool water is less than 7.2 and its total alkalinity is high, don’t add acid. Rather, wait for the pH to rise before continuing. If the pH doesn’t increase after a day or two, you must increase the pH before resuming.

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