How to Test Pool Alkalinity The Right Way
OLPO
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Facing the costly cycle of adding chemicals? You may wonder why does high alkalinity cause cloudy water. The answer is the pH imbalance, indeed, the most frustrating problem.
But the journey to a stable pool water begins by understanding the Total Alkalinity. Mastering the testing of total alkalinity is the most useful skill a pool owner can learn.
This guide will help you solve cloudy water and imbalanced water issues step-by-step to achieve a clear pool.
What is Total Alkalinity & Why Does it Matter?
Total Alkalinity is the most underrated parameter in the swimming pool that can disturb the pH and ultimately the water chemistry.
By definition, the total alkalinity is the water's buffering capacity. The carbonate ions have the ability to neutralize acids. The ideal range is 80-120 ppm and can be adjusted based on the type of sanitizers.
If the TA is not correctly balanced, the pH will fluctuate steadily, leading to pH bounce and pH lock.
The pH bounce (when TA is too low) can damage metal components as the water becomes corrosive.
The pH lock (when TA is too high) can promote calcium buildup on surfaces and result in cloudy water.
Choosing Your Tools: The Test Kit Showdown
There are multiple TA testing methods depending on the accuracy, cost, and ease of use. We will help you find the best one by comparing each.
Method
Accuracy
Ease of Use
Cost
Best For
Test Strips
Low to Moderate
Very Easy
Low
Quick, frequent checks for a general overview; users prioritizing convenience over precision.
Liquid Reagent Kit
High
Moderate
Moderate
Precise weekly balancing; users demanding reliable data before adding chemicals; the "gold standard" for DIY management.
Digital Tester
Very High
Easy
High
Users prioritizing maximum accuracy and eliminating subjective color interpretation; ideal for data tracking.
Hybrid Testing Strategy
For home pool owners seeking to achieve accuracy on budget, a hybrid testing strategy is the most practical solution.
Use the test strips for routine monitoring (2-3 times weekly) to detect any chemical shifts. Plus, use an expensive liquid kit once weekly to obtain high-precision results.
Pro Tips: The Cyanuric Acid (CYA) Complication
Sometimes, an artificially inflated reading can occur if the pool is sanitized with stabilized chlorine tablets like Trichlor or Dichlor. Since these stabilized chlorine products come with CYA, this introduces additional ions affecting the true "Carbonate Alkalinity".
Even if you see a high TA result, the buffering capacity would still be lower. That is why most home kits show different results compared to the pool supply stores.
How to Test for Total Alkalinity with Liquid Reagent Kit
Want to know how to test alkalinity in a pool accurately? Let's get down to the titration method step-by-step.
Step 1: Collect a Proper Sample
Your water sample must be the true representation of the entire pool; therefore, mastering water collection is the core here. Run the pump for at least an hour to circulate the water before testing.
Always collect water from the deep, middle of the pool (away from skimmers and jets) where the water is chemically balanced and free of dirt. If possible, dip a clean bottle upside-down deeper to 12-18 inches using the elbow-deep method. Conduct the test as soon as possible.
Step 2: Prepare the Test Vial
Take the large test vial and rinse it with the previously collected water several times. Fill it up carefully to the precise line indicated for the TA test.
For maximum accuracy, neutralize the chlorine first with a drop of specific reagent (often Sodium Thiosulfate). Then add the required drops of indicator reagents and swirl gently. The sample water here should start turning green or purple.
Wait for chlorine to return to normal range post-shocking treatment to avoid excessive interference.
Step 3: Perform the Test (The Titration)
Add final titration reagents (typically sulfuric acid), one drop at a time, while holding the bottle vertically for uniform drop size. Honestly, this part needs critical testing where you have to count every drop of the reagent. Swirl the vial gently and observe the colour shift from green to a vibrant red.
Step 4: Calculate Your Result
Now, multiply each counted drop by 10 to calculate the end result. Like for 10 drops, the TA would be 100 ppm. Dispose the water safely (not back into the pool) and clean the vial.
Mastering Pool Chemistry: Alkalinity's Central Role
Explore the ultimate guide on Pool Chemistry Cheat Sheet
Why You Must Adjust Alkalinity Before pH
The golden rule of "Alkalinity First" is the cornerstone of professional water balancing. A stable TA acts as the anchor to support a stable pH. The carbonate ions in TA consume the excessive hydrogen ions that come from the addition of acidic sanitizer or acid rain, preventing the pH bounce.
Why Your Pool's pH Keeps Rising (The Role of Aeration)
The acid-base balance is not as simple as it looks.
When the alkalinity is medium to high, it results in the buildup of carbonates in the pool. These carbonates may convert to carbonic acid during CO2 outgassing, which happens due to aeration ( through waterfalls, jets, fountains, or even splashing). This disturbs the acid-base equilibrium.
So to get back what was lost, the reservoir of bicarbonate ions converts to carbonic acid, which splits into water and CO2. As a result of this, pH rises steadily.
The moral of the story is that frequent acid addition is necessary to maintain the pH.
What Should Your Alkalinity Actually Be? (A Guide by Sanitizer Type)
Set the ideal TA target depending on the type of sanitizer you choose. The goal is to naturally push the pH to avoid pH bounce or pH lock.
Sanitizer Type
Effect on pH
Recommended TA Range (ppm)
Rationale
Liquid Chlorine, Cal-Hypo, Saltwater Generators (SWG)
Raises pH
80–100
A slightly lower TA moderates the natural upward pH drift from these sanitizers.
Trichlor Tablets, Dichlor, Bromine
Lowers pH
100–120
A higher TA provides a stronger buffer to resist the constant downward pH pressure.
Having robotic pool cleaners or skimmers can make your chemical balancing efforts more fruitful. Because when the pool is physically cleaned at all times, there will be no debris buildup, ensuring a more stable water and a healthier pool overall.
How to Raise or Lower Your Alkalinity
When the alkalinity level is not in the target range, here is how you can fix it.
To Raise Low Alkalinity
If the Total Alkalinity is below 80 ppm then the best chemical fix is Sodium Bicarbonate (NaHCO3).
The rule of thumb is that 1.5 lbs of sodium bicarbonate per 10,000 gallons of water raises TA by about 10 ppm. Following the dosage, turn the pool pump on to dissolve the broadcasted powder across the deep ends.
After running the pump for a good six hours, retest the TA and adjust as needed.
To Lower High Alkalinity
In case the Total Alkalinity is above 120 ppm and the pH is resistant to being reduced, then add pH-reducing chemicals. Most commonly used acids are Muriatic Acid (a liquid solution of hydrochloric acid) or Sodium Bisulfate (a granular dry acid). It is better to add in small dosages and follow the walk-down method to avoid a sudden pH crash.
While the pump is running, add a measured acid dose to lower the pH to 7.0-7.2. After circulating for a few hours, aerate the pool to force CO2 out of the water to raise the pH back without raising the Total Alkalinity.
Retest once pH is stabilized to 7.4-7.6. Repeat the process if the TA is still too high.
Final Words
An ideal TA and a stable pH create a stable chemical environment. Depending on your budget and technical comfort, you can use both testing kits or liquid reagents, with the latter one requiring more precision. Use alkalinity increasers (i.e., Sodium Bicarbonate) if TA is too low, and pH reducers (i.e., Muriatic acid or Sodium Bisulfate) if TA is too high.
Test regularly to get desirable Total Alkalinity levels. Maintain pool cleaning at all times to avoid frustrating chemical balancing efforts.