Iíve proven to myself that an alkalinity of 80 ppm or greater will require acid additions once or twice a week. The pH will rise from 7.4 to 8.2+ in 7 to 10 days. So if I maintain the pH between 7.4 and 7.8 I need to add acid at least once per week. If the alkalinity is 40 ppm acid additions are required about every 6 weeks to 2 months to maintain the pH between 7.4 and 7.8.
Iíve repeated the testing twice and got the same results both times. Iím now lowering the alkalinity to 40 and plan to keep it there unless there is some overriding reason to maintain a higher level.
The thing that bothers me is the recommendations and discussion on this site about maintaining the alkalinity at 70 to 100 ppm. Iím convinced that the pH in my pool is much more stable at a lower alkalinity than is recommended but I donít know why.
Is there some other factor involved in maintaining a stable pH or a reason besides pH stability for keeping the alkalinity higher?