How to Lower pH Level in Your Pool Safely

Written by Michael Dean
February 7, 2024

ph scale next to a swimming pool

If you are struggling with maintaining the chemical levels in your pool, you are not alone. Many homeowners struggle with basic pool water chemistry, and how to balance pH level is typically at the top of their problems.

A spike in your pool’s pH can cause many issues, be it reducing the effectiveness of your chlorine or causing skin rashes. Luckily, there are a few ways to fix this problem. In this extensive guide, I detail the safest way to lower the pH level in your pool.

Main Takeaways

  • High pH levels are caused by shocking the pool, high total alkalinity, improperly measured chemicals, and carbon dioxide loss.
  • If your pH is too high, it may cause irritation to swimmers, scaling, poor water quality, and may lower chlorine efficiency.
  • To lower the pH level in your pool, you can use either sodium bisulfate or muriatic acid.
  • Make sure to wear proper protective gear when lowering your pH levels.

What Causes High pH Levels?

The normal pH level to shoot for in a pool is between 7.2 and 7.6, but I usually consider 7.4 the optimum pH. However, you shouldn’t worry if this value isn’t exactly 7.4. It’s perfectly normal for your pool’s pH to fluctuate occasionally.

pH scale

However, you should be concerned if the value frequently goes beyond 7.8. High pH levels mean your pool’s water is very alkaline. Alkaline water can cause several problems in your pool, so staying on top of your pH level is important.

Water pH is extremely unstable, and many factors contribute to its surge. Below are the most common causes.

Pool Shock

Shocking your pool is vital for sanitizing the water, but you should only do so when necessary. Overshocking is possible and can cause chemical instabilities in your water. To shock the pool, pool owners use chemicals like calcium hypochlorite, sodium hypochlorite, and sodium Dichlor.

If you use calcium hypochlorite (cal hypo), you need to be extra careful. Although cal hypo is neutral, its pH can surge past 10 when mixed with water.

Runaway Alkalinity

High total alkalinity (TA) levels can raise your swimming pool’s pH. TA functions as a buffer that inhibits pH fluctuation. However, you should carefully pick the chemicals you use to increase the alkalinity of your pool.

Most individuals use sodium carbonate (soda ash) to increase TA. The problem with sodium carbonate is its high pH of 11.3-11.6. This range may increase the pH levels of your pool.

Improperly Measured Chemicals

To maintain a pool’s chemical balance, you must use the right chemicals and, more importantly, the right amounts of chemicals. Excess quantities might cause either high or low pH levels.

Carbon Dioxide Loss

From my experience, the loss of carbon dioxide (CO2) from pools can account for high pH levels. This is generally the most common contributing factor to high pH in a pool. Carbon dioxide transforms into carbonic acid when it dissolves in water. The pH of this acid is low, meaning it lowers your pool’s alkalinity.

The CO2 concentration in water should be similar to that in air. Carbon dioxide dissolves into and out of the pool’s water until an equilibrium is reached.

The primary cause of carbon dioxide loss is the presence of algae in water. Algae consume CO2 and, in doing so, prevent the formation of carbonic acid. Other factors that may cause CO2 loss in pool water include splashing and aeration. Water features are a huge contributor to CO2 loss, so if your pH is rising out of control, turn off the waterfall!

You Have Recently Replastered Your Pool

Replastering a pool is a necessary maintenance task that many pool owners will have to do at some point. However, new plaster can cause your pH levels to rapidly rise. This is because plaster creates a chemical called calcium hydroxide as it cures, which has a high pH of 12. There isn’t much you can do to avoid this while your plaster cures other than be vigilant with adjusting your pH levels.

You Have a Saltwater Pool

Saltwater pools work differently than standard chlorine pools, and the electrolysis process in which chlorine is formed from salt can create byproducts with very high pH levels. To avoid overly high pH, make sure you adjust your salt cell. If the problem persists, I recommend contacting a professional to check your salt chlorine generator.

What Happens If pH Is Too High?

You’ll encounter many problems if your swimming pool’s pH constantly rises.

Unhealthy to Swimmers

High pH levels in a pool can be a health hazard to swimmers. Swimmers might experience the following:

  • Red, irritable eyes
  • Dry skin
  • Skin rashes

Besides the health effects, a surge in the pool’s pH affects swimming gear. You’ll notice premature wear and tear of swimming suits and goggles.

Lowers Chlorine Efficiency

Chlorine becomes less effective when the pool’s pH levels are high. When chlorine interacts with water, it forms hypochlorous acid. This acid is responsible for inactivating all pathogens in water.

Hypochlorous acid functions best in acidic conditions. If your pool’s alkalinity is too high, hypochlorous acid will not kill all the microorganisms in your pool.

You have to find a median pH safe for swimming and doesn’t curtail the effectiveness of hypochlorous acid.

Causes Scaling

High alkalinity makes pool water hard. Hard water is susceptible to creating scale formations from calcium deposits. The build-up of scales may block or clog your pool’s pipes and filters and damage your salt cell in a saltwater pool.

Clogged filters and pipes affect water circulation and may significantly strain your pool equipment. Your pool might face issues like motor failures or even leaks. In the end, you incur considerable costs in replacing pool equipment.

Poor Water Quality

High pH levels affect the water quality in your pool. As mentioned above, chlorine is less effective in killing algae when the water is very alkaline. Very high pH also affects the solubility of chemicals like calcium. You’ll notice cloudy water if such chemicals don’t dissolve.

I recommend testing your pool before and after adding chemicals. The key things to check are pH, total alkalinity, and acid demand.

How to Lower pH Level in Your Pool: Two Strategies

If you notice high pH levels, you should work immediately to restore the right balance. There are two chemicals you can use to lower pH levels in pools. These two products are:

  • Sodium bisulfate
  • Muriatic acid

The industry term for these products is pH reducers. Some brands refer to them as pH minus. When shopping, you must be familiar with both products because muriatic acid is more potent than sodium bisulfate.

Muriatic Acid

Muriatic acid is an impure form of hydrochloric acid. It’s a caustic acid with a pH of about 1-2. Homeowners mostly use it to wash tiles, clean bricks, and clear drains.

As a pool owner, you can use this acid to offset high pool pH levels. You can use my pH calculator to determine how much you need to add. Read my article on does muriatic acid lower pH for instructions on how to use it, too.

Is It Safe?

Muriatic is a very corrosive acid. It is capable of corroding anything, be it clothing or metal.

This acid is safe for home use, provided you take safety measures and follow the manufacturer’s instructions. And you’ll need to wait a while before swimming if you add muriatic acid to your pool.

How to Lower pH Levels Using Muriatic Acid

If you suspect your pool’s pH is high, it might be time to add muriatic acid.


Muriatic acid comes in liquid form. It can burn your skin at the slightest contact, and its fumes can affect your respiratory system. You should handle this acid using full protective gear.

I recommend the following materials:

  • A chemical-resistant apron
  • Acid-resistant gloves
  • Chemical fume protective mask
  • Safety goggles
  • A plastic bucket
  • A stirrer (wooden or plastic)
Acid Blue Muriatic Acid by CPDI - Swimming Pool pH Reducer

This is a simple muriatic acid that I use in my swimming pools all the time.

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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Once you’re ready, follow this guide.

Step 1: Test the Pool’s PH

Your pool’s pH range should be between 7.2-7.6. If it’s higher, consider lowering it using muriatic acid.

When testing the pH, you can use test strips, differential sensors, or process sensors.

Step 2: Wear Protective Gear

Before handling muriatic acid, you must wear protective clothing. I urge you to wear acid-resistant gloves, safety goggles, an acid mask, and a chemical-resistant apron. Make sure the apron covers your legs and arms. And don’t forget to wear close-toed shoes.

Step 3: Measure and Dilute the Muriatic Acid

The manufacturer’s instructions should indicate the ideal amount of acid to use. You may need to dilute muriatic acid before adding it to the pool. Diluting the acid makes it less dangerous if it splashes. Always add the acid to the water in the bucket and not water on the acid.

Step 4: Turn on the Pump

Turning the pump on or off is a matter of preference. Some claim that when the pump is on, it adds oxygen to the acid and amplifies the pH levels.

However, I recommend turning the pump on due to the strength of the acid. Muriatic acid might corrode the pool floor if left too long in one section.

Step 5: Add the Muriatic Acid

Walk around the pool while slowly pouring the acid. Concentrate more in the deep end of the pool. After you’re through, rinse off the bucket.

Step 6: Give It Some Time

It may take up to 30 minutes for the acid to disperse into the pool water. During this period, no one should enter the pool.

Step 7: Re-check the pH Levels

Re-test the water after 3-4 hours to ensure optimal pH levels. If they are off, add more muriatic acid until you achieve the ideal levels. Don’t jump into the pool until the pH level is safe for swimming!

Sodium Bisulfate

Sodium bisulfate is another common way to lower the pH of your pool. This chemical is a dry acid that forms when sulfuric acid reacts with a base like sodium hydroxide or sodium chloride. Although reactions between acids and bases yield neutral products, sodium bisulfate is only partially neutralized. It has an acidic pH of about 1.

Sodium bisulfate has many names. You may also know it as dry acid, bisulfate of soda, sodium hydrosulfite, sodium hydrogen sulfate, sulfuric acid, sodium salt, monosodium hydrogen sulfate, acid salt, or niter cake.

Is It Safe?

Sodium bisulfate is a safer product compared to muriatic acid. It comes as a fine powder, so be cautious when using it in windy conditions.

How to Lower pH Levels Using Sodium Bisulfate (pH Decreaser)

When it comes to the maintenance of a swimming pool, sodium bisulfate primarily acts as an acidity regulator. Sodium bisulfate also goes by many other names: dry acid, pH decreaser, pH down, or pH minus are all common names you’ll see. But it’s all the same thing! You use it to curb the runaway pH levels of your pool water.


Avoid using sodium bisulfate during windy conditions. The wind can easily blow this fine powder back into your eyes, hands, or skin.

A few things you’ll need include:

  • A pool test kit
  • A plastic bucket. Do not use metallic containers
  • A stirring rod (wooden or plastic)
  • Safety equipment like gloves and glasses
  • A measuring cup (plastic)
  • Sodium bisulfate
  • A plastic scoop
Leslie's Dry Acid

You can get Leslie's Dry Acid (sodium bisulfate) online if you don't have a Leslie's Pool Supplies store near you.

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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Once you’re set, follow these steps.

Step 1: Test the pH

It’s always advisable to test your pool water before applying pH reducers. The ideal pH range should be between 7.2 to 7.6. If you find the pH is above 7.6, proceed and use sodium bisulfate.

Step 2: Decide the Quantity to Add

The quantity you should add depends on the pool size and the manufacturer’s instructions. It may also depend on how high your pool’s pH is.

I recommend only adding three-quarters of what the manufacturer suggests. You’re unlikely to add excess dry acid if you follow this rule.

Step 3: Add the Sodium Bisulfate

Once you measure the ideal amount, pour the powder into the pool near the return jets. Avoid adding sodium bisulfate near the skimmer.

Some manufacturers advise pre-dissolving sodium bisulfate in a bucket before adding it to the pool. If you decide to do so, ensure you add the dry powder to the water and not the other way around. Pouring water onto the powder can cause chemical boiling, which can be harmful.

Afterward, turn on the pool to evenly distribute the sodium bisulfate granules. If you don’t have a pool pump, you can use a paddle to circulate the water manually.

Step 4: Allow the Sodium Bisulfate to Dissolve

Dry acid doesn’t work instantly. It needs time to dissolve before it does its job.

Step 5: Re-Test the Pool’s pH

After waiting for several hours (about six hours), re-test your pool’s pH. If the levels are still high, you must repeat the entire process. This time, ensure you add the sodium bisulfate slowly.

What If the pH and Alkalinity Won’t Balance?

Don’t panic if your pH and alkalinity levels are still out of whack after you have adjusted them. Pool chemistry is a complex animal and takes time and patience to get right. It is very easy to bring down your pH level, but in the process, you have brought your alkalinity down too much, or vice versa! While alkalinity and pH are related, they are not the same thing, so when you adjust your chemical levels, they will be affected in different ways.

Muriatic acid and sodium bisulfate will affect both your pH and alkalinity, so what do you do if you only want to lower your pH?

My recommendation for lowering your pH level without affecting your alkalinity is to use a carbon dioxide injection. As I mentioned above, a loss of carbon dioxide can cause your pH to rise rapidly. You can use a pure CO2 system, or contact a pool professional to assist you.

The same method works the other way around as well. If your pH level is too low, you can use an oxygen aerator to raise the pH without significantly raising the alkalinity.

Safety Tips

It’s advisable to exercise caution when adding muriatic acid and sodium bisulfate to your pool. Always ensure you:

  • Wear protective gear
  • Don’t mix these products with chlorine; such a combination produces toxic fumes
  • Add the acid into a bucket of water and not the other way round
  • Only use three-quarters of the recommended portions
  • Do not use the pool for a few hours after adding pH reducers
  • Use plastic buckets

And that’s about it. Don’t be intimidated by either method to lower your pool water’s pH level. If you overshoot it, make sure to check out my article on how to raise the pH level in your pool.

A Few Tips to Keep Your pH Balanced

Your pool’s pH level is not permanent and will inevitably change over time. As a pool owner, you will need to adjust these levels often. But here are a few tips to keep the pH balanced and help minimize the frequency of needing to lower the levels.

Test your pool water frequently. pH levels can change very quickly based on many different factors. So, consistently checking the levels is imperative.

Keep your pool clean and sanitized. A clean pool is less likely to have issues with chemical imbalances.

Shock your pool only when necessary. High amounts of chlorine can cause the alkaline levels to rise high. This is why you should only shock your pool when it is necessary.

Check your tap water. Not all water is created equal. Tap water in some areas has high mineral content and could have a higher pH level.

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Frequently Asked Questions

Does baking soda lower pH in your pool?

Baking soda is an alkaline chemical used to raise the pH level of your pool water. It is used to improve the clarity of your pool when you have a pool below 7.2 to 7.6 pH.

Can you lower pH in your pool naturally without adding more chemicals?

There are a few methods you can use to naturally lower the pH in your pool. The first is to heat the pool. Doing so will lower the pH levels, thereby increasing the acidity of the water. The second option is to simply leave the water alone. The pH in your pool water should naturally decrease. Alternatively, you can simply do a partial drain and refill, but this will only work if your tap water has a neutral pH.

Is the process for lowering pH in your saltwater pool any different?

The process of lowering pH in a saltwater pool is essentially the same as with a chlorinated pool. There are no real differences in the process. You just need to test the water and add a pH decreaser like muriatic acid or sodium bisulfate.

Can you swim in a pool with high pH?

Swimming in a pool over the recommended pH levels is not recommended, as excessively alkaline water can irritate your eyes, skin, and hair. Plus, chlorine disinfection will be much less effective in a pool with high pH, so you’ll also be swimming in some pretty dirty water!

Does pool shock lower pH?

No, it doesn’t. In fact, pool shock is more likely to raise pH levels. This is why you must check the pH levels before and after shocking – especially if you use cal hypo.

Does chlorine raise or lower pH?

It depends on the chlorine you should use. For example, trichlor is pretty acidic, so it tends to decrease the pH level. On the other hand, liquid chlorine and salt chlorine generators tend to raise the pH level. However, with that said, liquid chlorine and salt chlorine generators neutralize themselves in creating gas, effectively canceling their effect on the pH levels.

Keep Your pH Balanced!

Fighting the chemical levels in your pool can be tiring, but it is essential to balance your pH. High pH can spell out disaster, damaging your pool surfaces, causing a build-up of algae, and even harming swimmers. Stay vigilant with your testing and lower your pH level to the recommended level if the reading is above 7.6.

Any more questions about lowering your pH level safely? Feel free to reach out to me! I am always happy to help.

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