Understanding pH and How To Use It In Your Pool

We measure how acidic or basic water is by using the pH scale. The pH scale goes from 0 to 14, and is relative to pure water, at 7 pH ( neutral ). pH stands for “power of Hydrogen;” the measure of the concentration of hydrogen ions in a solution. 

When the concentration of hydrogen ions goes up, the pH goes down.  When the concentration of hydrogen ions goes down, the pH goes up.  

From a water chemistry perspective, the ideal pH for a swimming pool or spa is between 7.2-7.6. If your pH is higher (more alkaline), you can lower it by injecting carbon dioxide (CO2) or adding some muriatic acid. If your pH is lower (more acidic), you can raise it by adding soda ash or sodium bicarbonate (baking soda).

Managing pH is a critical component of maintaining healthy pool water. pH is a driving factor in the Langelier Saturation Index (LSI), and also because pH determines how effective chlorine will be. The lower the pH, the stronger chlorine will be. The type of chlorine you use affects both pH and total alkalinity. That’s because different types of chlorine have very different pH levels. For example, Trichlor (found in pucks) has a low pH. Calcium Hypochlorite (shock) has a high pH of almost 12. Liquid chlorine, sodium hypochlorite has a pH of 13.

Low pH can cause damage to pool liners and etching of plaster; corrosion of metal components in and around the pool; skin and eye damage, as well as general discomfort; and a reduction of total alkalinity.

High pH water can cause scale formation; metal stains; cloudy water; poor efficiency of chlorine, and also can cause skin and eye irritation.  Sodium bicarbonate (baking soda) is commonly used to raise both pH and total alkalinity.

What Is Alkalinity?


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Unlike pH—which is basically an equilibrium scale to measure against—total alkalinity is a measurement of the concentration of all alkaline substances dissolved in the water. These substances are primarily 1. carbonates, 2. bicarbonates and 3. hydroxides along with a few others). These alkaline substances buffer* pH in the water by neutralizing acids. In other words, total alkalinity is a measurement of the water’s ability to resist change in pH (Buffering capacity refers to water’s ability to keep the pH stable as acids or bases are added. If the water has sufficient buffering capacity, the buffering capacity can absorb and neutralize the added acid without significantly changing the pH. Conceptually, a buffer acts somewhat like a large sponge.)

Total alkalinity is measured by its concentration in parts-per-million (ppm), and the ideal range is from 80-120 ppm, depending on the type of chlorine you use. For example, Trichlor has a low pH of about 3, which means you will want your total alkalinity closer to 120 ppm, given how acidic Trichlor is. Liquid chlorine (bleach), however, has a high pH of 13, so you can have lower alkalinity, like 80-100 ppm.

Note: one of the byproducts of using liquid bleach (sodium hypochlorite) is sodium hydroxide, which contributes to total alkalinity and raises pH.

Total alkalinity is measured by the amount, or concentration (ppm = parts per million) in the water, not by how alkaline (basic pH) the water is. (Acidic is low pH; alkaline is high pH). ‘Alkalinity up’ products are prevalent in the pool industry. If you are in the market for an alkalinity increase, the two most common are sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3), more commonly known as soda ash. ‘Alkalinity down’ products will be an acid like muriatic acid or sodium bisulfate.

The Mixed Role Of Total Alkalinity And pH In Water

If you’re a pool operator, you probably already know that pH can fluctuate up and down. And when it does, the pool is constantly fighting against you. Having the right level of total alkalinity helps to keep the pH stabilized. A simple way to think about this is alkalinity neutralizes acids.

Alkalinity buffers pH by either providing or absorbing a Hydrogen ion (H+) as needed. 

If you want to increase total alkalinity add carbonates, bicarbonates or hydroxides to the water. As mentioned before, two of the most common pool products are sodium carbonate (soda ash) and sodium bicarbonate (sodium bicarb).

If you want to lower alkalinity use acid. Dilute the acid in a bucket of water, and evenly pouring it around the pool.

Maintain your pool within pH and alkalinity balance. Then, try to keep your total alkalinity within the range of 80-120 ppm for healthy pool chemistry. Use an alkalinity increaser like sodium bicarbonate to raise total alkalinity, or an acid to lower it. When using high-pH chlorines like liquid bleach or Cal Hypo, stay lower in the range, like 80-100 ppm. For low pH chlorines like Trichlor, 110-120 ppm is where you want to be.

The important role of CLEAN & CLEAR MINERALS with total alkalinity and pH in balancing pool and spa water

Adding the prescribed dosage of CLEAN & CLEAR MINERALS to your pool or spa should have a net zero effect on pH and alkalinity.

This is extraordinarily important when it comes to the health of your pool water. C-Pool CLEAN & CLEAR is all natural minerals that can have a huge impact on the clarity and health of your water without interfering with  the pH or alkalinity or balance. Pool owners have all the advantages of healthy water without having to take samples to the pool stores and paying for various chemical concoctions.