How to Lower Total Alkalinity and Adjust pH in a Swimming Pool
This article is for anyone who needs to lower high total alkalinity (TA) and high pH down to the recommended levels for a swimming pool. All you have to do is add muriatic acid to lower both totally alkalinity and ph, then aerate the pool to balance pH out. It usually takes me two days and two nights (a full 48 hours) to get the perfect balance of total alkalinity and pH. However, 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.
How to Lower Alkalinity and pH
- 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.
- Allow the pool water to aerate naturally without using any aerators such as spa jets, waterfalls, fountains, return pointers, air compressors, or the likes. Aeration helps bring up the pH level if it goes too low. The recommended level for pH is around 7.4 or 7.6.
- Take readings after six hours, then after 24, and then after 48 to make sure all chemicals are balanced. If you're lucky, and the pH level doesn't go below the normal range, then you do not need to do anything more.
- If pH levels are still too low after 48 hours, and you want to speed up the process, use an air compressor to accelerate the aeration process (optional).
Natural aeration (not using any equipment to speed up the process) is highly recommended, but 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 because over-aeration raises the pH levels and lowers the calcium carbonate levels beyond recommended levels, which can cause significant damage to the pool.
What You'll Need
- Muriatic acid: The success of lowering alkalinity largely depends on the acid you use. I like using because it works very quickly. Some people use sodium bisulfate, but I find muriatic to be the most effective. Wear goggles, gloves, and long sleeves when working with this substance or any other chemicals. Sunnyside Muriatic Acid
- Accurate pool water test kit: I prefer the digital water test kit. 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 out there are not accurate and will make your job more difficult. LaMotte ColorQ Pro 11
- Aeration: This is not a tool or chemical but a process that restores pH levels. (Don’t get tense. It's not rocket science!). pH levels may go down after a strong acid like muriatic is added, so aeration is needed to restore the recommended pH levels naturally without adding a pH increaser, which increases alkalinity.
Ideal TA and pH Levels
• Your target TA should be 100 ppm. TA in the 80-120 ppm is considered balanced.
• 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 to do this. 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 as an example to help you understand this process.
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 would drop way below 7.0 when I add a strong acid, so my experience told me that 100 ppm was 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 the 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.
The natural process of 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.
Step 4: Test the Pool Water's Alkalinity and pH After 6 Hours
You will be watching for the changes in pH and alkalinity levels by doing a test after every 6 hours until it reaches the right range. If pH is within the normal range after adding muriatic acid, then you are done.
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, total alkalinity read around 205 ppm (down from the original 280 ppm) 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. I didn't worry too much about this because according to my digital pool water test kit and pool calculator, the lowest it pH can go is 6.8 and still be okay and non-destructive. Plus, the aeration process wasn't finished.
Since both chemicals were within a reasonable range, all was 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 the "magical" aeration process is still going on.)
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, pH levels will not likely rise above the recommended levels because the alkalinity is within range and no pH increaser was used in this process.
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. When carbon dioxide mixes with water, it forms an acid we call carbonic acid, which lowers the pH levels. On the other hand, when acid is removed from the water, the pH level rises. Aeration literally removes carbonic acid from the water, which then raises the pH levels.
I always recommend natural aeration because 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 because it prevents the plaster from dissolving. In the 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 more 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).
Other Common Problems With Total Alkalinity and pH Levels
- If your pool has a high level of pH but total alkalinity is OK, pick up pH Reducer and get it down to recommended levels (between 7.2 and 7.8). And remember not to use muriatic acid in this case, since it will lower your TA. I always use liquid by Kem-Tek, which is always very effective and quick compared to other brands. pH Minus
- If you already know you have low pool alkalinity but pH is OK, get some alkalinity increaser to bring it back up to the recommended levels, and do it fast to avoid corrosion. by Pool Mate is one of my best options, since it is effective and pocket friendly. I have used it ever since I started in the pool service business, and I have never changed to any other. 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
- If your pH is high and alkalinity is low in the same water, you may need to add pH reducer/minus and then alkalinity increaser to your pool to lower pH and increase alkalinity respectively.
- 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 further lower pH down to very dangerous levels for a swimming pool. In this case, the best thing to do first is to use to raise the level of pH without raising your TA, and then carefully add muriatic acid to lower both. This product is the most effective one I've found, and I use it for my clients. It is a better option than pH increaser/plus since it does not affect other chemicals in the pool but only increases pH. 20 Mule Team Borax
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.
Should I Use Soda Ash and Baking Soda to Raise pH?
Last month, 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. Some parts of the internet recommend this as a quick fix, but don't do it!
Soda ash and baking soda raises alkalinity to abnormal levels, which in turn also increases the pH to a disproportionate amount. When I checked my friend's 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.
How Does High Alkalinity Harm Your Pool?
- 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 that causes calcium scaling and comes as a result of high pH levels.
Can You Safely Swim in a Pool With High Alkalinity?
As long as you have enough chlorine in your pool (around 3ppm for total chlorine) and the pH level is balanced (between 7.4 to 7.8), then a pool with high total alkalinity is still safe to swim in. You should, however, balance TA as soon as possible because it can lead to calcium scaling and cloudy water—a breeding ground for bacteria.
Summary of Key Points
- Total alkalinity should only be lowered when it causes 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.
At what Level do you Maintain your pH
Questions & Answers
My pool is 5500 gallons. The alkalinity is 427 ppm and PH 8.5. I put one gallon of muriatic acid and tested the water after 24 hours, and there was no difference in the levels. The free chlorine is 0.05 ppm. Should I add another gallon of muriatic acid, or should I shock it, wait 24 hours and then add more acid?
I checked my pool, and the pH just right, but the alkalinity is high. What kind of solution should I put in the pool?
You need to add Muriatic acid to reduce the TA, but remember that any acid will lower the level of the pH too. So the best thing is to add Muriatic acid to the pool to lower the TA down between 100 - 125 ppm, then add 20 Mule Team Borax to raise the pH to the recommended levels between 7.2 and 7.8. This might take a couple of days, remember to take accurate readings while fixing the problem.