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Fixing Total Alkalinity and pH Problems in Your Swimming Pool

Updated on April 6, 2017
Barack James profile image

Barack is a chemical engineer and pool water chemistry nerd. He has been in the commercial pool maintenance industry for more than 7 years!

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How To Reduce Total Alkalinity and pH Levels: No Extra Equipment

If you have tried all the crude pool chemistry recommended by your friends to reduce total alkalinity (TA) in your pool, but things seem to be getting worse, then you have come to the right place.

It does not cost much to reduce total alkalinity and pH from high status to recommended levels. Apart from an accurate digital pool water test kit that may be a little pricey, all you will need is muriatic acid and a natural process known as aeration. (Don’t tense. It's not rocket science.)

I have included everything I did step by step. It took me two days and two nights (48 hrs) to get the perfect balance of pH and total alkalinity. I used muriatic acid without using any aerators such as spa jests, waterfalls, fountains, return pointers, air compressors, or the likes.

This process needs patience as it may take a day, two days, one week, or even longer, depending on how extreme the pH and TA levels are. If you need faster results, at the end of this article I have included all the equipment to help speed up the process.

How to Balance TA and pH Levels in a Pool

 
 
Step 1
Take accurate readeings of TA and pH using a reliable test kit.
Step 2
Dilute muriatic acid and distribute it evenly in the pool. Use a pool calculator to get the exact amount of acid needed. Your target TA level should be 100 ppm.
Step 3
Take readings after 6 hours, then after 24, then after 48.
Step 4
Allow the pool water to aerate to help balance the pH level. The recommended level is around 7.5 ppm or 7.6 ppm.
Step 5 (optional)
Use an air compressor to accelerate the aeration process.

Step 1: Take Accurate Readings of pH and TA in the Pool

I take accurate readings using the LaMotte ColorQ Pro 7 digital pool water test kit. From my personal testing, the pH read 8.3 ppm and total alkalinity read 280 ppm.

Very Important Note

You need a very accurate test kit for this process. The more accurate your readings are, the easier your work will be. Most of the test strips available on the market are not accurate and will make your job hell.

Step 2: Set a Target Value for Total Alkalinity

I set the target value of TA at 100 ppm. 80 ppm or 90 ppm should be fine, but I anticipate that the levels of pH will drop below 7.0 ppm when I add strong acid.

Use a pool calculator to calculate the exact amount of muriatic acid needed in order to achieve the target 100 ppm for TA.

In this step, don't worry too much about the pH. The main aim is lower total alkalinity to recommended levels. Later on, you can aerate to raise pH levels.

Step 3: Dilute Muriatic Acid as Directed and Add It to the Pool

The pool I was working with was 20,000 gallons. To get my target value of 100 ppm, I added about 2 quarts of muriatic acid. I distributed the muriatic acid solution slowly around the pool while the pump was running high to increase the effect.

Some pool managers prefer adding muriatic acid solution in one spot. Personally, I don't like to do this because acid can damage pool parts when it is concentrated in one region.

Step 4: Test the Pool Water After 6 Hours

Amazingly, when I tested the water 6 hours later, total alkalinity was reading at 205 ppm from 280 pmm and pH was at 7.6 ppm from 8.3 ppm.

Step 5: Take the Readings After 24 Hours

The following morning at 10 am, around the same time I started the operation a day before, total alkalinity had gone down to 120 ppm. This was not the target value I set, but I was still impressed since it was already within the recommended value for a standard swimming pool. On the other hand, pH was getting lower and it was reading 7.1 ppm. This didn't worry me a lot because according to my digital pool water test kit, the lowest it can go is 6.8 ppm, which is still okay and won't be destructive.

Since both chemicals were still within a reasonable range, I decided that nothing else needed to be done. So I waited to take my next reading in the evening, approximately 5 to 6 hours later. When I took the reading in the evening, TA was ranging at 106 ppm, and the pH dropped to 6.9 ppm. You can imagine how impressive that was. This meant that total alkalinity was inching closer to my target value, despite pH going down. Again, don't worry about the pH because you can balance it later using the 'magical' aeration process.

Step 6: Take Final Water Test 48 Hours Later

After two days and two nights of keeping a close watch over the pool, I took the reading in the morning. Total alkalinity was reading 101 ppm — not bad at all. The pH was stable at 7.4 ppm. Remember that even if the aeration process is not complete, the pH level will unlikely rise above the recommended levels because the alkalinity should be within range and no pH increaser is used in this process.

Note

If your results are different from mine, it may be that you are using poor quality test strips. You will have to take accurate readings of TA and pH again. Then use the pool calculator and repeat the entire process until you get your TA and pH in the correct balance.

At what Level do you Maintain your pH

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Overview of Aeration: Balancing Total Alkalinity and pH

Aeration is a complicated chemical process. It involves pointing the returns upwards and running the pump on high to create surface disturbance, which introduces air. You must go through this process until the perfect natural equilibrium is reached between water and air at the surface. If interested, here is the detailed theory behind the aeration process of balancing pH and TA.

How the Aeration Process Works

  1. You start by adding muriatic acid as needed in the affected pool. Then you must repeat this step until you get a perfect chemical balance. This will lower both the pH and total alkalinity.
  2. In most cases, when total alkalinity goes up, pH will likewise drift up as well. However, there is no chemical available that can lower alkalinity and pH at the same time and rate, and then only raise pH without also raising total alkalinity. (How I wish chemical engineers could invent that kind of chemical.) In other words, if you lower a pH of 8.3 ppm to the recommended level using muriatic acid, the total alkalinity will also reduce but will still remain on the higher side. Likewise, if you lower alkalinity to the recommended level (e.g., from 300 ppm to 80 ppm), the pH level drops below the recommended level.
  3. If you add a strong acid like muriatic, and then add a base like soda ash to raise total alkalinity, it will not work. This is because both chemicals (base and acid) will cancel each other, leaving your pool in the same initial mess.
  4. Therefore, aeration is a repetitive process that is done slowly and step by step. Your goal is to use muriatic acid to reach the target value of total alkalinity without letting pH go below 6.8 ppm. If the pH falls, you can raise it without affecting total alkalinity by aerating.

Accelerating the Aeration Process Using an Air Compressor

Using an air compressor will add additional air to create surface disturbance and speed up the process. You can use an air compressor with an end tube that has several tiny holes in it. Place it in the deep end. The small bubbles that escape from the holes produce carbon dioxide, which is released into the atmosphere to accelerate the aeration process. Do this with the pump running high. With an air compressor, it may take only a few hours to get TA and pH back to recommended levels.

Other Recommended Ways to Accelerate Aeration Process

  • Use a degasser to remove carbon dioxide faster.
  • Use venture injectors.
  • Use manifolds with holes.
  • Use a pressure washer aimed into the water to create turbulence.
  • Use return lines that are aimed up (e.g., waterfalls or spillways).

Facts to Know

  • A high TA level has a potential indirect risk of affecting how all chemicals function in a pool. For instance, the pH — one of the most important chemicals in the pool — is hugely affected by total alkalinity. When alkalinity goes too high, the pH will drift to the higher end and this will render all chemicals in the pool useless, including chlorine.
  • On the other hand, when the TA goes too low, the pH will drift down. This is very destructive to the pool structure and equipments, as well as harmful to human health.
  • High total alkalinity is also associated with calcium saturation index (CSI), a process which causes calcium scaling and comes as a result of high pH levels.

Personal Experience

I manage my swimming pool myself and such cases of high pH and alkalinity are not common thanks to my efforts. About a month ago, a close friend of mine who has a plaster pool informed me that he had a huge drift in pH. I came to realize that he was using soda ash to increase the pH whenever it dropped below the recommended level, and baking soda to raise TA.

Soda ash raises alkalinity, just like baking soda does. This caused total alkalinity levels to increase, which in turn also increased the pH. When I checked his pool, it was at 8.2 ppm and was scaling up higher day by day. Total alkalinity was reading well over 280 ppm when the recommended values should be between 80 ppm and 120 ppm. Luckily, the calcium level did not scale as expected due to the calcium saturation index — it was within the expected range of 250 ppm. Calcium scaling causes cloudy pool water.

Conclusion

Total alkalinity should only be lowered when it is causing a significant rise in pH levels, or when it causes calcium scaling through CSI.

To lower pH and total alkalinity, use a strong acid such as muriatic acid, sulfuric acid, or sodium bisulfate, all of which lower both pH and TA, but at different rates. You need to use an accurate pool water test kit that can give you correct readings. If possible, find a software that can help you get exact amounts of dry acid to add into the pool.

This process may take longer than anticipated, depending on how high pH or total alkalinity is, and how low you need to bring them down before the aeration process begins. However, you can always use an air compressor or any other aerator to accelerate the process.

If you have achieved the ideal reading for total alkalinity but the pH is scaling up because the process of aeration has not yet ceased, you can use Borate to keep the pH stable. The recommended level for pH is around 7.5 ppm or 7.6 ppm.

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