How to Lower Pool pH

Have you noticed an odd tingling on your skin, your eyes stinging, or your swimwear and pool surfaces developing a chalky residue? These could be signs that your pool’s pH is too high.

But before you start pouring in a bunch of chemicals to fix it, it’s important to understand what’s causing the imbalance in the first place. Adding more chemicals without addressing the root issue can actually make your water quality worse. 

Unstable Alkalinity 

Alkalinity acts as a stabilizer for your pool’s pH, helping keep it in the ideal range (usually 7.2 to 7.6). It’s made up of minerals like calcium and magnesium, as well as bicarbonates and carbonates. These components work by absorbing extra acidic or basic ions, which helps prevent sudden pH swings.

When alkalinity levels drop, your pool loses this stabilizing power, making it much easier for even small amounts of acidic or basic substances to throw the pH off balance. If alkalinity isn’t sufficient, pH can shift too high or too low more easily, causing issues with water balance and pool comfort.

Low CO2 levels

When CO₂ dissolves in water, it combines with H₂O to form carbonic acid (H₂CO₃). This weak acid on dissociation releases hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻). The hydrogen ions (H⁺) released make the water more acidic, thereby lowering the pH.

But that’s not all. The bicarbonate (HCO₃⁻) created through this process acts as part of a buffer system that keeps pH stable. Here’s how:

• When the pool water gets more acidic (lower pH), the bicarbonate can absorb excess H⁺ ions, preventing the pH from dropping too low.
• When the pool water becomes too basic (higher pH), bicarbonate can release H⁺ ions, lowering the pH.

So if CO₂ escapes from the water (e.g., from aeration, excessive usage, or splashing), there’s less carbonic acid and fewer hydrogen ions. With fewer H⁺ ions in the water, the pH will rise, making the water more basic and unsuitable for swimming. 

You can use a CO₂ meter to monitor the levels and keep the pool covered to minimize CO₂ loss when not in use. 

Water Hardness Level

In some regions, water is naturally hard, meaning it contains higher levels of minerals, particularly calcium and magnesium, along with calcium carbonate—a major contributor to pH spikes in pool water.

When you add hard water to your pool, the calcium carbonate it contains interacts with the water by releasing carbonate ions (CO₃²⁻). These carbonate ions actively bind to hydrogen ions (H⁺) in the water. Since hydrogen ions play a key role in keeping pH low, reducing their presence removes an essential buffer, causing the pH to rise.

In short, each time hard water enters the pool, it introduces more calcium carbonate, which continually releases carbonate ions that consume hydrogen ions, gradually pushing the pH higher.

Too Much Baking Soda 

Alkalinity is the natural buffer for pool water, helping maintain stable pH levels and overall chemical balance. When it falls out of the ideal range (80 ppm to 120 ppm), it throws the pH and other chemical levels out of balance as well. To fix this quickly, many pool owners turn to baking soda, a common solution for raising alkalinity.

However, there’s a catch: Baking soda is basic in nature with a naturally high pH. 

While it can effectively increase alkalinity, it also has the potential to raise the pH along with it. This isn’t ideal if your pool’s pH is already high, as adding baking soda could make the issue worse. 

So, it’s essential to use it sparingly and keep an eye on your pH levels. If you’ve noticed a recent pH spike after using baking soda, now you know why – it’s the baking soda’s basic nature at work.

Electrolysis in Saltwater Pools

Saltwater pools often experience higher pH levels because of the electrolysis process that generates chlorine. When salt (sodium chloride) is converted into chlorine, it also produces sodium hydroxide – a substance with a very high pH, which can raise the pool’s pH if it builds up.

This buildup happens when the salt-chlorine generator runs for extended periods, especially if it’s overworked to keep up chlorine levels. To prevent this, it’s best to limit the salt cell’s operation to 8-10 hours per day during peak season to avoid excessive sodium hydroxide accumulation.

High Water Temperature

When water temperatures rise, gases like carbon dioxide (CO₂) become less soluble and escape more easily. Since CO₂ forms carbonic acid, which helps keep pH stable, its loss leads to reduced acidity and a higher pH, making the water more alkaline.

Additionally, higher temperatures speed up chemical reactions, causing chlorine and other sanitizers to break down faster. This shift can also push the pool’s pH upward as the chemical balance changes. 

One simple way to keep the temperature stable is by pulling the pool cover over when it’s not in use. 

High Bathing Load

When people jump into your pool, they bring organic materials along – think sweat, oils, lotions, and even hair products. These contaminants can interact with chlorine and other sanitizers, causing shifts in water chemistry that may drive up pH levels. Essentially, the more swimmers you have, the greater the chance of contamination and subsequent pH imbalances.

To help mitigate this issue, consider installing an outdoor shower near your pool. It’s a simple yet effective way to keep the water quality in check.

Drain and Refill

Draining and refilling your pool is a practical method for lowering pH levels, especially when the pH isn’t drastically high. However, it works best if your new water has a neutral pH between 7.2 and 7.4.

However, this method does come with some drawbacks:

• Requires Chemical Rebalancing: After a significant water change, you may need to rebalance your chemicals. This often means adding chlorine and stabilizers, and adjusting alkalinity, making the process lengthy and potentially costly.
• Not Always Recommended: Because of the effort involved, this method isn’t generally advised unless you already plan to partially drain and refill your pool for other reasons –  like removing substances that don’t break down over time, such as excess salt or calcium.

CO2 Injection

Next on our list is CO₂ injection, a method that replenishes the carbon dioxide lost from your pool water. This approach is one of the most natural and safe ways to lower your pool’s pH without disturbing the overall water chemistry or relying on harsh chemicals.

Instead of using aggressive substances to force the pH down, CO₂ injection targets the root cause – CO₂ loss. It is a colorless and odorless gas that’s easy to handle, posing minimal risk as it requires no special protective equipment.

One of the key benefits of CO₂ injection is that it doesn’t introduce secondary pollutants like chlorides or sulfates into the water. Instead, it helps maintain chemical balance by forming carbonates and bicarbonates. When dissolved, CO₂ lowers pH gradually, allowing for controlled adjustments that keep your pool’s water chemistry stable.

Steps Involved:

• Set Up the CO₂ System: Place the CO₂ tank and regulator near your pool equipment in a well-ventilated area. Connect the regulator to the CO₂ tank, then attach the dosing line to an injector or diffuser positioned in the pool’s return line or skimmer.
• Configure Control Options: For automated systems, allow the controls to adjust CO₂ injection rates based on real-time pH readings. For manual systems, test pH regularly and adjust the CO₂ flow as needed to stay within the ideal range.
• Adjust Initial pH Levels: Begin by testing your pool’s pH (target range: 7.2 to 7.6). Slowly introduce CO₂ into the water. As CO₂ dissolves, it creates a mild acid that helps lower pH without heavily impacting alkalinity. Wait a few hours, then retest the pH. Adjust CO₂ flow if necessary to reach the desired level.
• Maintain Stable pH Levels: Check pH at least weekly, especially after heavy pool use or adding chemicals, and adjust CO₂ injection rates based on test results to maintain stability.

   

Using Sodium Bisulfate

Next to Co2 injection, using sodium bisulfate or dry acid to lower your pool’s pH is the safest and most eco-friendly method. 

When added to water, sodium bisulfate releases hydrogen ions, which help neutralize the water’s alkalinity, gradually bringing down the pH. This mild acid approach reduces pH without significantly affecting the pool’s total alkalinity, keeping the water balanced and preventing corrosion of pool equipment.

As the name suggests, it needs to be stored in a dry place, away from any moisture, to keep it from clumping or losing its effectiveness. Also, always wear gloves when handling it, as it can irritate the skin.

Steps Involved:

• Test the Current pH: Start by testing your pool water using a reliable test kit or strips. This will give you a baseline to determine how much sodium bisulfate you need.
• Calculate the Amount Needed: To lower the pH by 0.1 in a 10,000-gallon pool, you’ll need about 1 pound (16 ounces) of sodium bisulfate. For exact amounts, refer to the product label or use an online dosage calculator based on your pool’s size and current pH.
• Dissolve and Add the Chemical: In a bucket, mix the calculated amount of sodium bisulfate with about 5 gallons of water until it’s fully dissolved. This helps prevent concentrated acid from damaging your pool surfaces. Pour the solution near the return jets or in the deep end to ensure even distribution, and avoid adding it directly to skimmers or localized spots.
• Circulate the Water and Re-test: Run your pool pump for at least 4–6 hours to circulate the water thoroughly and allow the sodium bisulfate to lower the pH effectively. After 8-10 hours, test the pH again. If it’s still higher than the ideal range of 7.2 to 7.6, repeat the process in smaller increments until you reach your target pH.

Adding Muriatic Acid

Muriatic acid, though effective for lowering pH, is generally our least preferred method due to its hazardous nature. It is highly corrosive and can cause severe burns on the skin, eyes, and respiratory tissues if not handled carefully. The fumes can be irritating and even harmful when inhaled, so using it in a well-ventilated space is essential. 

Additionally, overuse or incorrect dosing risks damaging your pool surfaces, plumbing, and equipment, making this a chemical that should be handled with caution.

Steps Involved:

• Test the Water: Start by measuring your pool’s pH and total alkalinity using a test kit. This gives you a baseline for how much muriatic acid you’ll need.
• Calculate the Correct Amount: Determine the amount of muriatic acid required based on your pool’s size and the current pH level. As a general rule of thumb, add 1 quart (of 15% strength) for a 15,000-gallon pool. This will reduce the pH by 0.1 units. 

• Dilute the acid: Although not always required, you can dilute muriatic acid by adding it to a bucket of water (10 parts water to 1 part acid). Always pour acid into water – not the reverse – to avoid splashing.

• Add the Acid to the Pool: Turn on the pool pump for circulation and slowly pour the diluted acid into the deep end or near the return jets while walking around the pool edge. Be careful not to splash or let acid come into direct contact with pool surfaces.
• Let the Pump Circulate the Water: Keep the pump running for at least 4-6 hours to help the acid mix evenly throughout the pool.
• Re-test the pH: After a few hours, test the pH again. If further adjustment is needed, repeat with a smaller amount.

Test Regularly: Check your pH levels at least 2-3 times a week, especially after heavy use or rain. Reliable test kits are your best friend for getting accurate results. Also, keep an eye on total alkalinity (aim for 80-120 ppm) since low alkalinity can make pH levels swing up and down.

Ensure Good Water Circulation: Run your pool pump for 8-12 hours daily to keep water moving, which helps spread chemicals evenly and keeps pH levels stable. Don’t forget to clean or replace the filter regularly to keep everything flowing smoothly.

Stay on Top of Cleaning: Skim out leaves, dirt, and other debris often so they don’t break down and mess with your water chemistry. Give the pool walls a good brush and vacuum the bottom weekly to prevent algae buildup that can also affect pH.

Shock the Pool When Needed: Shocking your pool every 4 weeks (or after a lot of use) helps clear out contaminants and stabilize chlorine. Choose a shock treatment that won’t throw off your pH.

Mind the Swimmer Load: Heavy use can introduce all kinds of stuff into the pool that affects pH. Encourage guests to shower before diving in to keep extra debris to a minimum.

Add Chemicals Slowly: When tweaking pH or alkalinity, add chemicals gradually and retest after each addition to avoid overshooting. For low alkalinity, using a pH stabilizer like sodium bicarbonate can help buffer pH changes.

Watch Environmental Factors: Warmer water speeds up evaporation and CO₂ loss, which can push pH higher. Adjust your chemical treatments as needed and cover your pool when it’s not in use to reduce evaporation and keep out debris.

Dealing with high pool pH doesn’t always have to mean pouring hydrochloric acid into your water and handling hazardous fumes. 

Sometimes, a simple solution like draining your pool halfway and refilling it with stable, soft water can do the trick. CO₂ injection is another great option – though it can be a bit pricier, it’s safe, easy to manage, and won’t mess with your water chemistry.

If those methods don’t fit your needs, dry acid is a good alternative. Just try your best to steer clear of muriatic acid! While it promises quick results, it can throw your water chemistry out of balance and pose safety risks.