Camcarb is proud to announce that we now offer CO2 delivery services for swimming pools to balance and control pH levels.
Why Should I Use CO2?
CO2 is the best alternative to using muriatic acid (hydrochloric acid) to balance pH levels in chlorinated water. It's safe, reliable and helps to improve your pool's comfort and safety. The CO2 is regulated by an automatic control system which means less hassle for the operator.
What Benefits Do I Get from Using CO2?
CO2 raises the alkalinity of the water, thus forming a natural buffer that helps to prevent your pool's pH from suddenly dropping.
By maintaining constant optimum pH levels, your pool will be have improved clarity, a reduction in chemicals use, safer conditions for swimmers, and the pool surfaces will incur less damage.
Using CO2 also helps to eliminate the use of dangerous acids in your pool and as well as their costs associated with their use.
1. Understanding CO2
Carbon Dioxide (CO2) is a common compound that is found everywhere, including the air we breathe. Even though our atmosphere is only 0.03-0.06% CO2, pools will still absorb this gas from the air. Once absorbed, a small amount it reacts with water to form carbonic acid, a slightly acidic compound which contributes in lowering the pH of water.
2. CO2 and Water
The amount of CO2 in pool water has a direct impact on the pH. The more CO2 there is, the lower pH, and the less CO2 there is, the higher the pH. Water that contains no CO2 has a pH around 8.4, whereas water saturated with CO2 has a pH near 5.
CO2 in pool water doesn’t just come from the air, it can also be introduced by adding acid. When acid is added, not only does the pH go down but so does the alkalinity. This is because the acid reacts with the bicarbonate alkalinity buffer to create carbonic acid.
3. Henry’s Law - Why pH Levels Rebound
When acid is added to pool water, the pH initially goes down because extra CO2 is formed. Later on, the pH tends to rise and return to previous levels in order to balance and satisfy the equilibrium relationship between the CO2 in the water and the CO2 in the air. This relationship, known as Henry’s Law, dictates that the extra CO2 formed by the acid must off gas back into the atmosphere, thus gradually raising the pH but not the alkalinity.
4. CO2 and Calcium Scaling
Dissolved CO2 in pool water helps to keep calcium deposits soluble. Therefore it is desirable to maintain pH levels in the mid to high 7 range. At the same time, pH levels that are too low can be harmful to pool plasters and pH levels that are too high can create problems with scaling.
5. CO2 Systems
When CO2 is added to pool water, either by pure CO2 injections or by adding dry ice, the pH drops but the alkalinity isn’t affected.
Systems designed to use CO2 in conjunction with a sanitizer such as bleach are becoming popular. This method uses CO2 to offset the high pH of the bleach and works quite well to keep the pH in balance. The only downside is the gradual increase in alkalinity over time due to the small alkaline properties of bleach. However, small amounts of acid can be added to control alkalinity and this method doesn’t require large amounts of harsh acids and offsetting amounts of sodium bicarbonate or soda ash to maintain the pool’s quality.
Because CO2 will escape from the water over time, it needs to be continually added to keep the pH from rising.
6. Pool Covers
Non-gas permeable pool covers are designed to prevent the exchange of gases between air and water. In new plaster pools, if the natural off gassing process is blocked, the CO2 in the pool will react with the hydroxide component of the pool’s plaster surface and form carbonate. This not only depletes the CO2 in the water but it causes the pH to rise. If the cover is not removed to allow the CO2 to dissolve back into the water the pH will continue to climb and cause solid calcium and scale to appear in the pool.
In fiberglass, vinyl, and painted pools, where hydroxide isn’t present, pool covers help keep the pH low by inhibiting any CO2 that’s been introduced into the water from escaping into the air.
When pools have non-permeable covers the pH needs to be carefully monitored to ensure the gases are properly equilibrated and the pH is balanced.
7. Factors in CO2 Off Gassing
Many factors work together to determine the rate at which CO2 off gases. These include: temperature, alkalinity, atmospheric pressure, circulation, and the ratio of water volume to air-exposed surface.
Higher water temperatures, increased circulation and aeration all contribute to accelerate off gassing. Conversely, low temperatures, circulation, and aeration will slow down the process and reduce the speed at which the pH rebounds. Other factors such as high alkalinity and a pH above 8.4 promote absorption of CO2 back into the water and lowers the pH.
8. CO2 and Reducing Alkalinity
Traditional methods of reducing alkalinity involve the quick addition of large amounts of acid (which often lowered the pH below the ANSI/APSP minimum of pH 7.2) or the slow, laborious process of adding small amounts of acid over hours and days until the desired alkalinity was reached.
A much better way of reducing alkalinity is to add acid while increasing aeration and surface exposure. The use of jets, air bars, and fountains create air bubbles and increases exposure to air, thus rapidly increasing the rate at which CO2 off gases. This method allows the alkalinity to be reduced very quickly without having the pH drop below undesired levels.