How to Lower Total Alkalinity and Adjust pH in a Swimming Pool
The Simplest Way to Reduce Total Alkalinity and pH Levels
This article is for anyone who needs to reduce both excess Total Alkalinity (TA) and pH down to the recommended levels for a swimming pool.
Secondly, if you already know you have low pool alkalinity but pH is OK, get some to bring it back up to the recommended levels, and do it fast to avoid corrosion: TA should be kept between 80 and 120 ppm for pools with liners and between 100 and 125 ppm for pools made of plaster. alkalinity increaser
Thirdly, if your pH is high and alkalinity low in the same water, you may need to add pH reducer and then alkalinity increaser to your pool, to lower pH and increase alkalinity respectively.
On the other hand, if your pool has high total alkalinity and high pH and you have tried all the methods you know to lower both TA and pH in your pool but nothing works, then you have come to the right place. All you will need is...
- Muriatic acid. The success of lowering of alkalinity largely depends on the acid you use. I like using since it works very fast. Sunnyside Muriatic Acid
- A very accurate pool water test kit. I prefer the digital water test kit. LaMotte ColorQ Pro 11
- A natural process known as aeration. (Don’t get tense. It's not rocket science!). Since your pH level will drift much lower after a strong acid like muriatic is added, aeration is needed to restore the recommended pH levels naturally without adding a pH increaser that also increases alkalinity. However, if you happen to be lucky that pH level doesn't go below the normal range (7.2 to 7.8) for a swimming pool, then your work will be complete at this point.
On the other hand, in very rare cases, your total alkalinity may be high but with a low pH in the same pool; if so, using muriatic acid directly to lower TA is not a good idea since this will farther lower pH down to very dangerous levels for a swimming pool.
Alternatively, you can naturally aerate (use an aerator if natural aeration is taking longer) your pool while the pump is on 24/7 to raise the level of pH up between 7.6 and 7.8 or higher, which might take a couple of days, and then lower both the TA and pH using muriatic acid slowly and carefully while watching on the pH levels not to go very down: Repeat the process until you get the required levels for both total alkalinity and pH - Keep reading for more instructions about aeration.
It usually takes me two days and two nights (a full 48 hours) to get the perfect balance of total alkalinity and pH. I use muriatic acid and then aerate naturally without using any aerators such as spa jets, waterfalls, fountains, return pointers, air compressors, or the likes. Below, I have included everything I do, step by step.
This process needs patience as it may take a day, two days, one week, or even longer, depending on how extreme the TA and pH levels are high in your pool.
However, if you need faster results, at the end of this article I have included a list of equipment that will help speed up the process and instructions for how to use it. Extra care must be taken to avoid over-aeration if you decide to use aerators.
How to Reduce & Balance TA and pH Levels in a Pool
Take accurate readings of TA and pH using a reliable test kit.
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.
Take readings after 6 hours, then after 24, then after 48.
Allow the pool water to aerate to help bring up the pH level if it goes too low. The recommended level for pH is around 7.4 or 7.6
Step 5 (optional)
Use an air compressor to accelerate the aeration process.
Your target TA is 100 ppm
Your target pH level is around 7.4 or 7.6
Step 1: Take Accurate Readings of pH and TA in the Pool
I always use a LaMotte ColorQ Pro 7 digital test kit. Let's say that the pH reads 8.3 and total alkalinity reads 280 ppm, which are the real values from a pool I worked on last. Your readings may be higher or lower, but let's just use these numbers for this example to help you understand this process step by step since I was recording every little improvement I made in the process.
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 are not accurate and will make your job more difficult.
Step 2: Set a Target Value for Total Alkalinity
In the same example above, I set my target value of TA at 100 ppm. It is important to note that both the levels of TA and pH reduce when acid is added. A target value of 80 ppm or 90 ppm should be just fine, but I anticipated that the levels of pH will drop way below 7.0 when I add a strong acid, so my experience told me that 100 ppm is ideal for raising the level of pH later on through aeration.
Use a pool calculator to calculate the exact amount of muriatic acid you will need in order to achieve the target value of 100 ppm for TA, or whichever target value you have chosen.
In this step, don't worry too much about the pH yet. The main aim is to lower the total alkalinity to recommended levels. Later on, you can aerate to raise pH level if it goes much lower than is recommended.
Step 3: Dilute Muriatic Acid as Directed and Add It to the Water
The pool in my example holds 20,000 gallons. To get my target value of 100 ppm, I needed to add about 2 quarts of muriatic acid.
I usually distribute the muriatic acid solution slowly around the pool while the pump is running high to increase the effect.
Some pool managers prefer adding the 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.
Aeration begins after you add the muriatic acid and the levels of pH and TA have fallen and settled. During the aeration process, the levels of pH alone will rise gradually until it reaches the recommended level. You will be watching on the changes in pH level by doing a pH test after every 6 or 12 hours until it reaches the right range. But if pH is withing the normal range after adding muriatic acid, then you are done.
Step 4: Test the Pool Water's Alkalinity After 6 Hours
Taking the reading after six hours is just to help you know whether you are making any improvements in lowering the TA and pH. Amazingly, when I tested the water six hours later in my example, total alkalinity read around 205 ppm (down from the original 280 pmm) and pH was at 7.6 (from where we started at 8.3). Your numbers may be different, but you should see a similar reduction in your process too.
Step 5: Take Readings Again After 24 Hours
The next day, a full 24 hours since I started my test, the total alkalinity had gone down to 120 ppm. This is not the 100 ppm target value I set, but I was still impressed since 120 ppm is already within the recommended value for a standard swimming pool.
On the other hand, pH was lower, reading 7.1. This dint worry me much because according to my digital pool water test kit and pool calculator, the lowest it could go was 6.8, which is still okay and won't be destructive.
Since both chemicals are still within a reasonable range in my example, all is fine for me. So I waited to take my next reading in the evening, approximately 5 to 6 hours later. At that time, TA was ranging at 106 ppm, and pH had dropped to 6.9.
This means that total alkalinity was inching closer to my target value of 100, despite pH going down. (Again, don't worry much about the pH yet, 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 process, I took the reading in the morning. Total alkalinity in my example read 101 ppm—not bad at all. The pH was stable at 7.4. Remember that even if the natural aeration process is not complete, the pH level will unlikely rise above the recommended levels because the alkalinity is within range and no pH increaser was used in this process.
At what Level do you Maintain your pH
How Does Aeration Increase pH Levels?
When you aerate, you are exposing the water to more oxygen in order to do away with some of the carbon dioxide.
As you may know, carbon dioxide mixed with water forms an acid we call carbonic acid, and any acid added to water will lower the pH levels. On the other hand, when acid is removed from the water, the pH level will rise. So aeration literally removes carbonic acid from the water, which then raises the pH levels.
I always recommend natural aeration since with this method, you cannot over-aerate your pool, which is a very common issue when aeration equipment is used.
As a matter of fact, over-aeration is dangerous since you need some carbonate to act as a pH buffer. Carbonate is useful in plaster pools since it prevents the plaster from dissolving. In a case of over-aeration, pH will rise above the recommended levels while calcium carbonate will reduce below the required level. To fix this, you'll need to adjust the pH and calcium carbonate levels to avoid any further damage.
Overview of Aeration: Balancing Total Alkalinity and pH
Aeration is a complicated 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.
How the Aeration Process Works
- You start by adding muriatic acid as needed in the pool. This will lower both the pH and total alkalinity. You must repeat this step until you get a perfect chemical balance.
- In most cases, when total alkalinity goes up, pH will drift up as well. Unfortunately, there is no pool chemical that can raise pH only without raising total alkalinity—maybe one day chemical engineers will invent that kind of chemical :) In other words, if you lower a pH of 8.3 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 way below the recommended level.
- 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.
- Aeration is a repetitive process that is done slowly, 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. 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 at the surface of the water will add additional disturbance and speed up the process.
- Try 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 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).
Helpful Facts to Know
- A high TA level has the 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 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's 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.
What About Soda Ash and Baking Soda? My Personal Experience
I manage my swimming pool myself and 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.
The problem is that 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, pH was at 8.2 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.
Summary of Key Points
- 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 water test kit that can give you correct readings. If possible, find software that can help you get exact amounts of dry acid to add into the water.
- 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 7.4 or 7.6.