Baking soda, also known as sodium bicarbonate, is a common ingredient used to help maintain swimming pools. There are several reasons why baking soda is an important part of pool care and maintenance:
To Raise pH Levels
One of the primary reasons baking soda is added to pools is to raise the pH level. Properly balanced pool water should have a pH between 7.4-7.6. If the pH drops below 7.2, it can cause damage to the pool surface and equipment. It can also irritate the eyes and skin of swimmers. Baking soda has an alkaline pH, so adding it to pool water will bring up low pH levels.
How Baking Soda Raises pH
When baking soda is dissolved in water, it forms sodium ions (Na+) and bicarbonate ions (HCO3-). The bicarbonate ions react with hydrogen ions (H+) in the water to form carbonic acid (H2CO3). This reaction removes hydrogen ions, which decreases acidity and causes the pH to rise.
Ideal pH Range
Most pools function best when the pH is between 7.4-7.6. This helps sanitize the water properly, prevents damage and irritation, and keeps the water balanced. Baking soda gradually raises pH levels until the ideal range is achieved.
As a Buffer
In addition to raising pH, baking soda also acts as a buffering agent. This means it resists changes in pH, keeping levels stable in the ideal range. Buffering capacity is important for swimming pools because it prevents sudden spikes or drops in pH.
How Baking Soda Buffers
Baking soda contains both sodium ions and bicarbonate ions, which can react with hydrogen ions and hydroxide ions in the water. If the pH starts to drop and more hydrogen ions form, the bicarbonate will neutralize them. If the pH rises and more hydroxide ions form, the sodium ions will neutralize them. This push-pull reaction resists changes to the pH.
Prevents pH Fluctuations
Without adequate buffering capacity, the pH in a pool can fluctuate rapidly. As people swim, chemical treatments are added, and impurities build up, the pH would constantly spike outside the ideal range. The buffering from baking soda keeps the pH stable so it only requires occasional adjustments.
Helps Sanitization
Proper sanitization is critical for killing harmful bacteria and preventing diseases in swimming pools. Many common pool sanitizers, like chlorine, work best when the pH is between 7.4-7.6. Baking soda helps sanitize pools by ensuring the pH remains in this ideal range.
Improves Chlorine Efficiency
Chlorine is more effective at killing bacteria and algae when the pH is balanced. At lower pH levels, most of the chlorine is in the form of hydrochloric acid, which has very little sanitizing power. At the proper pH, chlorine exists as hypochlorous acid, which is a much stronger sanitizing agent.
Ideal for Other Sanitizers
Other common pool sanitizers like bromine and biguanides also work best at pH levels of 7.4-7.6. Baking soda works well with all these chemicals to improve sanitizing power across a range of pool treatment systems.
Softens the Water
In addition to affecting pH and sanitization, baking soda also helps soften pool water. Hard water contains high levels of dissolved minerals like calcium and magnesium. The softening action of baking soda helps prevent scale formation.
Reacts with Calcium
One way baking soda softens water is by reacting with calcium ions. It binds to the calcium to form calcium bicarbonate, which is more soluble and less likely to precipitate out as scale.
Reduces Mineral Deposits
By binding calcium and other minerals, baking soda keeps them dissolved in the water instead of depositing on pool surfaces. This helps prevent scale formation on tiles, plumbing, and equipment. Soft water also feels smoother for swimmers.
Extends Time Between Draining
Draining and refilling swimming pools can be costly and time-consuming. Baking soda helps extend the time between full draining by constantly working to balance pH, improve sanitization, and prevent mineral buildup. Well-maintained pools may only need draining every 5-10 years.
Slows Water Acidification
Over time, pool water naturally becomes more acidic due to the buildup of chemicals and contaminants. Baking soda counteracts acidification to slow the lowering of pH. This prevents the need for frequent draining and refilling.
Keeps Water Clarity High
By preventing pH fluctuations, scale formation, and mineral clouding, baking soda helps keep pool water clear and blue. Pool owners can go longer between complete draining when the water remains clean and usable.
How to Add Baking Soda
Adding baking soda to pools is a straightforward process. Here are some tips for using baking soda correctly as a pool additive:
Follow Manufacturer Guidance
Always check pool chemical labels for proper dosage amounts and instructions. Manufacturer guidance takes precedence over general rules of thumb.
Test and Adjust Gradually
Only add small amounts of baking soda at a time and then retest pH before further additions. It’s harder to lower pH after overshooting the ideal range. Go slowly to find the right dose.
Pour Evenly Around Perimeter
For best results, distribute baking soda evenly into the pool water around the sides. Avoid dumping in one spot, which can temporarily spike pH in that area.
Use after Backwashing
It’s common to add baking soda after backwashing pool filters. This replaces trace minerals removed during backwashing to maintain buffering capacity.
Ideal Baking Soda Levels
Target baking soda concentrations will vary by pool size and other factors. Some general recommendations include:
| Pool Size | Baking Soda (ppm) |
|---|---|
| Less than 10,000 gallons | 80-120 ppm |
| 10,000-20,000 gallons | 60-100 ppm |
| 20,000-35,000 gallons | 40-80 ppm |
| Over 35,000 gallons | 30-60 ppm |
Test baking soda levels weekly and conduct regular total alkalinity tests to maintain proper concentration. Reduce frequency after levels stabilize.
Using Other pH Increasing Chemicals
While baking soda is a common pool additive, other chemicals like sodium carbonate and sodium borate can also raise pH levels. However, baking soda has some advantages:
More Soluble
Baking soda dissolves readily in water, even when temperatures are cool. Sodium carbonate is less soluble, so it takes longer to dissolve and adjust pH.
Higher Buffering Capacity
Compared to sodium carbonate, baking soda has greater buffering capacity to resist pH changes. Sodium borate buffers well but is more expensive.
Adds Total Alkalinity
In addition to affecting pH, baking soda contributes to total alkalinity levels, providing more stability and buffering capacity.
Risks of Improper Baking Soda Levels
Using too much or too little baking soda can negatively impact your pool. Some potential issues include:
Etching and Staining
If pH drops too low, acidic water can etch and corrode pool surfaces. Staining and scale also occur when pH is out of balance.
Eye and Skin Irritation
Unbalanced water can irritate the eyes, skin, and mucous membranes. This leads to red eyes, itchy skin, and discomfort for swimmers.
Poor Circulation
Improper pH and total alkalinity decreases sanitizer effectiveness and allows more algae and bacteria to grow. This can plug filters and hamper circulation.
Damage to Equipment
Acidic water corrodes metal components like pumps, rails, ladders, and drains. Scale formation from high pH clogs filters and erodes concrete and plaster.
FAQs
How often should I test pH and alkalinity?
Test pH and alkalinity at least once per week. Test more frequently if adding baking soda or after heavy rain, use, or backwashing.
What’s the easiest way to raise pH?
Baking soda is the quickest and easiest way to raise pH in pools. Simply dissolve and distribute around the perimeter.
Can I just pour baking soda in the pool?
You can sprinkle baking soda directly into the pool, but it’s best to first mix with water to dissolve. Pre-dissolving helps disperse it evenly.
How does temperature affect pH?
Warmer water temperatures allow baking soda and other chemicals to dissolve better. Colder temperatures make it harder to maintain proper pH.
Conclusion
Baking soda is an essential chemical for maintaining safe, comfortable pool water. It primarily functions by raising pH and providing buffering capacity. Properly balanced pH helps optimize sanitizer effectiveness, reduce eye and skin irritation, prevent scale and corrosion, and extend the time between draining and refilling. By understanding baking soda’s key role in water chemistry, pool owners can keep their water properly balanced.