Low Alkalinity

Low Alkalinity In Pool - How To Raise It?

Total alkalinity is a measure of pool water quality that can impact a whole range of other chemical levels. Fundamentally, it’s important to keep total alkalinity in check to maintain a healthy pH.

In this article, we will cover the ideal levels of total alkalinity, how to test your pool, the causes and problems of low levels, how you can increase them, and how to prevent low alkalinity in the future.

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Ideal Total Alkalinity Levels In Pools

The amount of total alkalinity in your pool works to stabilise the pH of your water and protects it from developing low pH. Some fluctuation in the pH of your pool water is to be expected even while maintaining adequate chemistry, and total alkalinity helps maintain balance when pH levels are disrupted.

The ideal levels of total alkalinity in your pool range from 80-120 parts per million (ppm). As long as your pool is reading somewhere within this range, you do not need to attempt to make alkalinity adjustments. If your pool’s total alkalinity levels are lower than 80ppm, you will need to take steps to increase your alkalinity to prevent side effects.

While less common, the reverse problem does sometimes occurs, namely high pool alkalinity.

Diagnosing Low Alkalinity Levels

Low alkalinity levels must be diagnosed by testing your pool water. Most basic testing kits for pool chemistry contain testing solutions for total alkalinity, such as a 4 in 1 Test Kit.

While we tend to recommend test kits that use vials of pool water and testing solutions for the most accurate results, you may prefer to use test strips for your pool. A set of 4 in 1 test strips makes a great option for those seeking ease of use when testing their pool chemicals.

Causes of Low Alkalinity

Low alkalinity is a somewhat common occurrence that happens to many people through regular use of their pool. Many natural factors lead to loss of alkalinity in a pool, including evaporation in the heat and water movement caused by your pump or swimmers.

Alkalinity may also decrease when you lose pool water through routine splashing and swimming. Refilling your pool with fresh water can offset the chemistry of your pool, including your total alkalinity.

An accumulation of rainwater also lowers the alkalinity of your pool in the same way, so expect lower alkalinity after a heavy rainstorm.

Sometimes, the chlorine products you use in your pool can have an alkalinity-reducing effect, especially when used in excess. Products with a high concentration of chlorine, such as shock treatments, often disrupt many elements of your pool’s chemistry, including the alkalinity.

Low alkalinity can also be caused by using an incorrect dose of an alkaline-lowering product. When making adjustments to your pool’s chemistry, it’s essential to follow product instructions so that you ensure the correct dose for your pool.

Problems Associated With Low Alkalinity

Low alkalinity in a pool will lead to a problem where the pH can drop quite quickly, as there is no longer any alkalinity to buffer it. Low alkalinity will lead to an unstable, low pH, and you will spend a lot of time trying to lift it back up to normal levels, only to see it drop again quickly.

Low pH can lead to many problems with your pool, most of which are associated with corrosive qualities of the water.

Swimming in water with a low alkalinity and low pH level can cause intense irritation to the skin and is known to cause burning when it comes in contact with the swimmer's eyes or nasal passages.

Low pH can also lead to the corrosion of pool equipment and other surfaces that come in contact with the water. Plastic equipment may show signs of etching and will begin to degrade even faster if left out in the sun after use. Metal surfaces exposed to low pH often show signs of discoloration and may develop tarnish or rust.

Having low alkalinity levels in your pool may also cause your chlorine to be less effective at sanitising your water. This is because most chlorine products rely on water with a stable pH to work efficiently, and low pH levels can cause degradation to your chlorine even when stabilisers are used.

How to Increase Pool Alkalinity

If your pool’s total alkalinity is too low, it will need to be increased through the use of alkalinity balancing pool chemicals.

Sodium Bicarbonate (Baking Soda)

The most common compound used for this is sodium bicarbonate, which may be found in your pantry in the form of baking soda. It has an alkalinity of 72.6%, which is very high.

Still, much more sodium bicarbonate is needed to adjust your pool’s alkalinity than you may have on hand for baking or household cleaning. Approximately 150 grams is needed per 10,000 litres of pool water to raise total alkalinity by 10 ppm.

We recommend this alkalinity increaser designed specifically for pools, which contains enough sodium bicarbonate to raise 55,500L of water by 10 ppm, and can be used in more concentrated doses for a greater increase.

Sodium Carbonate (Soda Ash)

Another popular option is soda ash. Soda ash contains 57.5% alkalinity, which is lower than baking soda. However, it is substantially cheaper than baking soda, so this may be the winner overall if you are looking for a cheap way to raise your pool alkalinity.

However, the soda ash will lift the pH by quite a bit more than baking soda. Therefore, it’s best used when both the alkalinity and pH are low.

You are better off using baking soda when your pH is fine and you just want to increase the alkalinity.

For more information, check out the differences between soda ash and baking soda.

Dosing Instructions

Whether adding sodium bicarbonate or sodium carbonate to your pool, you should dissolve it in a bucket of water and then distribute the product over as large of an area as possible to increase effectiveness.

These compounds are not effective when added to your skimmer basket because they have a hard time dissolving in concentrated areas, and may settle out in large amounts in your pump and filter. They will also cause a localised high pH in this equipment, which could cause corrosion.

After casting the product across your pool, you should allow your pump to run for 4-6 hours before testing your alkalinity level again. This allows time for the alkalinity increasing chemical to dissolve fully into your water and will produce the most accurate test readings.

Once you have retested your pool’s total alkalinity, you should decide if you need to repeat treatment, taking care not to add more sodium bicarbonate than necessary.

Alkalinity raising products typically cause an increase in overall pH (especially soda ash), so it is important to monitor this factor of your pool’s chemistry after adjusting how alkaline the water is. If your total alkalinity levels had been chronically low before this treatment, you may need to use a pH decreaser after you have restored your pool’s alkalinity.

It’s also important to note that most pools will not require a pH increase after you have made adjustments to your total alkalinity levels.

Preventing Low Alkalinity in the Future

It’s important to remember that occasional low alkalinity is a common occurrence in swimming pools that is caused by normal use and maintenance, or through exposure to natural elements such as sun and rain.

Because there are not many factors that are known to lead to rapid loss of pool alkalinity, low alkalinity can be challenging to prevent. Some pool owners choose to use small amounts of alkalinity-increasing products during regular pool maintenance to counteract the loss that happens through regular use. When taking this approach, it is important to avoid raising your total alkalinity too high, which can lead to other problems.

In order to prevent low alkalinity, we recommend raising your total alkalinity levels to 100 ppm during the time of treatment. This number is safely within the range of acceptable alkalinity levels, and allows room for your alkalinity levels to drop slightly before they are low enough to cause problems with pH.

If you continue to test your pool’s total alkalinity regularly, you will notice it dropping before the levels reach an amount less than 80 ppm, giving you ample time to add small amounts of sodium bicarbonate to maintain your water’s chemistry.


Low alkalinity is a normal occurrence in swimming pools that is fairly easy to correct once you have learned about the right products and found the dose necessary for your pool.

Do you have any questions about low alkalinity, or do you need help figuring out the correct dose of sodium bicarbonate for your pool? Leave us a comment below, we’d love to help!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.