What Causes High Alkalinity in Pools

When people ask me for advice on their swimming pools or spas on where they should start at the beginning of the season, I tell them that the most important critical parameter test to run for water treatment is the total alkalinity test because low or high alkalinity can make or break your pool water chemistry. What causes High alkalinity in a pool?

  • Cyanuric acid also called CYA or chlorine stabilizer raises TA
  • Liquid chlorine (or ‘sodium hypochlorite) has a high pH
  • High Alkaline fill water
  • Soda ash-pH control
  • Sodium carbonate-pH control
  • TA rises due to excess hydroxides left behind by calcium and sodium hypochlorite after oxidation
  • Aeration of pool

What are the Root Causes Of High Pool Alkalinity There are several reasons why swimming pools have high total alkalinity. It could be the water source of where your pool water is coming from. In some areas, waters innately have a high alkaline water level. Another reason for high alkalinity is you might be using too many chemicals like sodium bicarbonate (or baking soda), in an attempt to increase the alkalinity range of your pools. This article will explain how and why


High alkalinity in pools can disrupt water balance, leading to issues such as cloudiness, scaling, and ineffective sanitation. To maintain a safe and enjoyable swimming environment, it’s essential to address high alkalinity promptly.
In this guide, we’ll explore effective strategies for fixing high alkalinity in pools, restoring optimal water chemistry, and ensuring the well-being of pool users. By understanding the causes of high alkalinity and implementing appropriate corrective measures, pool owners can maintain clear, balanced water suitable for swimming and relaxation

What Causes High Alkalinity in Pool

According to the USGS– Alkalinity is not a chemical in water, but, rather, it is a property of water that is dependent on the presence of certain chemicals in the water, such as bicarbonates, carbonates, and hydroxides. A definition of alkalinity would then be “the buffering capacity of a water body; a measure of the ability of the water body to neutralize acids and bases and thus maintain a fairly stable pH level”

Understanding Alkalinity In Your Pool - Barrier Reef Pools
What Causes High Alkalinity in Pool

In technical language, Alkalinity rises because of excess hydroxides left behind by hypochlorite chlorines: sodium hypochlorite (liquid chlorine) and calcium hypochlorite (cal hypo). There is a minor net rise in Total Alkalinity when all things are fully oxidized in the pool water.

However, there is a more rapid rise in TA when chlorine doesn’t completely oxidize contaminants and instead combines with nitrogen compounds like urea and ammonia. This does away with the production of hydrochloric acid (HCl) from the chlorine that would otherwise lower the pH and alkalinity after oxidation. Instead, alkalinity climbs higher.

  • Cyanuric acid also called CYA or chlorine stabilizer is the most common pool chemical that raises total alkalinity.
  • Liquid chlorine (or ‘sodium hypochlorite) has a high pH
  • High Alkaline fill water- calcium carbonate produces high pH and alkalinity in source water added because of evaporation or splash out.
  • Soda ash or sodium carbonate-commonly used chemicals for raising the pH level in a pool.

You can reduce the total alkalinity in your pool with a strong acid, such as muriatic acid or sodium bisulfate (pH decrease). Pay attention to the directions on the bottle, measuring and mixing only what you need to bring your alkalinity levels back to the ideal range of 100 to 150 ppm which affects the safety and cleanliness of your water, as chlorine kills germs in this ideal range.

High alkalinity in pools can be caused by several factors:

  1. Use of Alkaline Products: Adding alkaline products like bicarbonates or carbonates to raise pH levels can inadvertently increase alkalinity as well.
  2. High pH Levels: Elevated pH levels can contribute to high alkalinity since alkalinity and pH are closely related. As pH rises, so does alkalinity.
  3. Hard Water: If the source water for the pool has high alkalinity, it can lead to elevated alkalinity levels in the pool itself.
  4. Cement or Plaster Leaching: Over time, cement or plaster surfaces in the pool can leach alkaline substances into the water, contributing to increased alkalinity.
  5. Carbonate Precipitation: When carbon dioxide outgasses from the pool water, carbonates can precipitate out, raising alkalinity levels.
  6. Lack of Water Replacement: Insufficient water replacement can lead to a buildup of minerals and alkaline substances in the pool, increasing alkalinity over time.
  7. Use of Alkaline Cleaning Products: Some cleaning products used in pool maintenance may contain alkaline substances, contributing to higher alkalinity levels if not used properly.
Balance Your Pool Water in 7 Easy Steps | How To Adjust Pool Chemicals
How to Fix High Alkalinity in Pools

Identifying the specific cause of high alkalinity is crucial for implementing effective corrective measures and maintaining balanced water chemistry in the pool. Regular testing and proper maintenance practices can help prevent and address issues related to high alkalinity.

  1. Excessive Use of Calcium Hypochlorite: Calcium hypochlorite, a common pool sanitizer, can raise both pH and alkalinity levels if used excessively.
  2. Carbonate Buildup from Carbonate-Based Pool Treatments: Some pool treatments contain carbonate compounds that, if overused, can contribute to elevated alkalinity levels.
  3. Inadequate Pool Circulation: Poor circulation can lead to localized areas of stagnant water where alkaline substances accumulate, increasing overall alkalinity.
  4. Weather Conditions: Environmental factors such as heavy rainfall or excessive evaporation can affect pool water chemistry, potentially leading to fluctuations in alkalinity levels.
  5. Landscaping Runoff: Runoff from nearby landscaping, especially if the soil is alkaline or contains alkaline amendments, can introduce alkaline substances into the pool water.
  6. pH Drift: Fluctuations in pH levels, particularly if they occur frequently or drastically, can impact alkalinity levels over time.
  7. Water Source Changes: Switching to a different water source for pool filling or topping up can introduce varying levels of alkalinity, depending on the source’s mineral content.
  8. Alkaline Pool Additives: Some pool additives, such as pH increasers containing sodium bicarbonate, can inadvertently raise alkalinity levels if not used judiciously.

Addressing high alkalinity in pools often involves a combination of corrective measures, including adjusting pH levels, dilution with fresh water, and using appropriate pool chemicals to balance water chemistry. Regular monitoring and maintenance are essential to keep alkalinity levels within the recommended range for safe and enjoyable swimming conditions.

High alkalinity levels naturally decrease over time on their own. However high total alkalinity can develop other issues, like high pH that leads to ineffective chlorine, which can lead to algae. So it’s often worth staying on top of high alkalinity issues before they cause more trouble in your swimming pool.

Adding an acid to a solution will lower the total alkalinity, but it will also lower the pH level. If the total alkalinity needs lowering without affecting the pH level, an acid is added, and straight after the water is aerated to raise the pH level without affecting the alkalinity.

What Causes Low Alkalinity in Pools?

  • Rain can be acidic
  • Increase in swimmer load
  • Topping your pool off with H2O that has low alkalinity after backwashing/wasting
  • Chlorine-Chlorine is acidic
  • High H2O evaporation-losing H2O can dilute TA
  • Pool H2O agitation-H2O agitation increases the loss of CO2 ………………………………………………………………………………………….Read more

How to Fix High Alkalinity in Pools

When pool alkalinity is higher than the ideal range, it can cause the pool water to have a cloudy appearance. The water will also start dumping the materials it absorbed onto your pool’s surfaces in a phenomenon known as “calcium scaling.” Scaling and cloudy water will cause any pool to look unattractive, but other problems exist too.

What you need to do is stabilize your pool H2O by finding the appropriate total alkalinity (TA). Alkalinity is the measure of a pool’s total amount of alkaline materials in the water. In other words, alkalinity is a measurement of the water’s ability to neutralize acids.

A Guide To Alkalinity In Your Pool - Barrier Reef Pools
How to Fix High Alkalinity in Pools

Low alkalinity in pools leads to dramatic spikes and dips in the pool’s pH levels, while high alkalinity leads to overly buffered pool water with pH levels that are difficult to adjust to a proper range that will stabilize the water’s chemistry.

Muriatic acid is a form of hydrochloric acid, which is a corrosive, strong acid. It’s available at most pool supply or home supply stores, it is readily available but is dangerous to handle so be careful slow, and patient.

  • Turn off your pool’s pump-Aeration can raise Alkalinity
  • Read the directions on the bottle-Follow instructions
  • Follow safe handling practices- Muratic is a great choice but use caution.
  • Pour the product into the water products need to be diluted
  • Broadcasted the acid evenly over the pool’s surface
  • After an hour or so, turn on the pool pump to mix H2O
  • Test the alkalinity and pH levels
  • Retest

Fixing high alkalinity in pools requires a systematic approach to rebalance water chemistry and restore optimal conditions for swimming. The first step is to test the pool water using a reliable water testing kit to determine the alkalinity level accurately.

Once high alkalinity is confirmed, several corrective measures can be taken. One common method is to lower alkalinity by adding an acid, such as muriatic acid or sodium bisulfate, to the pool water. This acid reacts with alkaline substances, reducing alkalinity without significantly affecting pH levels. It’s essential to follow manufacturer instructions and safety precautions when adding acids to the pool.

In addition to chemical treatment, increasing pool aeration can help lower alkalinity naturally. By introducing air into the water through jets, fountains, or air blowers, carbon dioxide is released, which can reduce alkalinity levels over time. Another approach is to partially drain and refill the pool with fresh water low in alkalinity. This dilution method helps lower alkalinity levels while also refreshing the pool water.

Regular monitoring of water chemistry is crucial throughout the process to ensure that alkalinity levels are within the desired range. Adjustments may need to be made gradually over time until the optimal balance is achieved. It’s also essential to address any underlying factors contributing to high alkalinity, such as excessive use of alkaline products or inadequate pool circulation, to prevent the recurrence of the issue. By taking proactive steps to correct high alkalinity, pool owners can maintain a safe and comfortable swimming environment for themselves and their guests.

Adjusting Alkalinity in the pool always takes the longest of any chemical adjustments whether you need to lower alkalinity or raise alkalinity it is a waiting game and should be done a little at a time over 6- 8 hours so you can nail the right range without jumping forward or backward. Patience is key!


When people ask me for advice on their swimming pools or spas on where they should start at the beginning of the season, I tell them that the most important critical parameter test to run for water treatment is the total alkalinity test because low or high alkalinity can make or break your pool water chemistry. 

  • Cyanuric acid also called CYA or chlorine stabilizer raises TA
  • Liquid chlorine (or ‘sodium hypochlorite) has a high pH
  • High Alkaline fill water
  • Soda ash-pH control
  • Sodium carbonate-pH control
  • TA rises due to excess hydroxides left behind by calcium and sodium hypochlorite after oxidation
  • Aeration of pool

 How do you fix High pH with Low Alkalinity?

Put pool filter on recirculate
Run pump
Add soda Ash or sodium bicarbonate to raise alkalinity
Evenly distribute powder on the pool’s surface by walking around the pool
Waiting at least 6-8 hours for retesting TA
Once the alkalinity reading is 80-120 ppm .………………………………………………………………. Read more

JimGalloway Author/Editor


USGS- Alkalinity and Water 


What is the recommended approach for fixing high alkalinity in pools?

Answer: The recommended approach involves testing the pool water to confirm high alkalinity levels, followed by the addition of acid to reduce alkalinity, increasing pool aeration, partial draining and refilling with fresh water, and regular monitoring of water chemistry to maintain optimal balance.

Question: Are there any natural methods for lowering alkalinity in pools?

Answer: Yes, natural methods such as promoting the growth of aquatic plants, utilizing biological filtration, and incorporating pH-buffering substrates like peat moss or driftwood can help lower alkalinity over time without significantly affecting pH levels.

Question: How can I prevent high alkalinity in my pool in the future?

Answer: To prevent high alkalinity in the future, it’s essential to maintain proper pool maintenance practices, including regular water testing, balanced use of pool chemicals, adequate water circulation, and timely water replacement to dilute accumulated minerals and alkaline substances.

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