Water Chemistry

• Swimming pool water contains chemicals that work together to ensure that the water's chemistry is well-balanced. For example, the most common pool water disinfectant is chlorine. Pool chlorine needs to be balanced so that it helps maintain the pool's pH level, which is controlled by various chemicals. Going hand in hand with pool pH is total alkalinity, which is a measurement of all of a pool's alkaline chemicals, including those like sodium carbonate. Proper total alkalinity levels buffer a pool's pH levels and helps to keep them stable.
  
  

Water Sanitation

• Chlorine or bromine can be used in a swimming pool as a disinfectant. Pools should have a chlorine level of 2 parts per million (ppm). However, 1 to 3 ppm of of pool chlorine is an acceptable range. Bromine pool disinfectants should be at 2 to 4 ppm, though 4 ppm is best. Bromine is similar to chlorine, but it's more stable and longer-lasting in swimming pools, though also more expensive. For outdoor chlorine-disinfected pools, a chlorine conditioner such as cyanuric acid should be paired with chlorine.
  
  

Stabilizing Chemicals

• Beside adding chlorine to a pool's water to maintain its water stability, pool owners will need to add several other chemicals from time to time. Sodium carbonate raises a pool's pH level, while muriatic acid (MA) lowers both it and total alkalinity. Sodium bicarbonate increases total alkalinity. Lastly, calcium chloride increases calcium hardness and makes the water harder. Too-soft pool water can cause pitting in the plaster surfaces of in-ground pools.
  
  

Importance of pH

• The importance of maintaining a proper pH level in a swimming pool cannot be overstated. Pool pH affects both water sanitation and water stabilization. If pH in a pool is too low (below 7.2), pool chlorine will quickly disappear. If a swimming pool's pH rises above 7.8, its chlorine will work very sluggishly or not at all, though it'll still be present in the water. A pool's pH level should be between 7.2 and 7.8, and 7.4 to 7.6 is ideal.
  
  

Chemical Amounts

• Add more chlorine to a pool to raise its chlorine disinfectant levels (the same goes for bromine). To lower swimming pool disinfectant levels, don't add disinfectant until it declines to recommended levels. Add 1 pound of sodium carbonate per 25,000 gallons of water to raise pool pH. Add 1 quart of MA per 25,000 gallons to lower pool pH. You need to add 3.5 pounds of sodium bicarbonate per 25,000 gallons to raise a pool's total alkalinity by 10 ppm.