On occasion it is possible, especially in freshly filled pools, to find that both total alkalinity and pH need to be adjusted. Typically, if one factor is high or low, the other will be as well. It is not unusual, however, to have a condition where one factor is high and the other is very low. In such a situation, adjusting the wrong factor first may cause a significant problem with the other, or worse - cause a problem such as corrosion of equipment or precipitation of calcium. If this occurs with a freshly filled pool, it may be worthwhile to wait about 24 hours before making any adjustments. This wait will generally result in some natural balancing of the water without added chemicals. This process is commonly referred to as allowing the water to come into equilibrium. If additional adjustment is still needed, it will require far less time or chemicals.
In cases where the pH is low and the total alkalinity is high, raise the pH first into the normal range of 7.2 - 7.8 and then lower the total alkalinity. When the total alkalinity is low and the pH high, raise the total alkalinity first and then reduce the pH.
In all cases, never add acid to the pool water if the pH is less than 7.2, even if the total alkalinity is high. Instead wait for the pH to rise first before proceeding. If the pH does not come up by itself after a day or two you will need to add some pH Up before proceeding.