Del. Admin. Code tit. 16, Department of Health and Social Services, Division of Public Health, Health Systems Protection (HSP), 4464, app B
Measure the pool water pH, alkalinity and calcium hardness. The pH must be 7.2 - 7.8. pH can be raised by adding sodium carbonate (soda ash) and can be lowered by adding carbon dioxide (CO2), muriatic acid or sodium bisulfate (dry acid). Using the 104 F pH scale for spa pools and the 76 F pH scale for other pools, use a straight edge to line up the pH and alkalinity readings. The point where this extended line intersects the calcium hardness line is the level of calcium hardness needed for the water to be balanced. Do the same for pH and calcium hardness to get the alkalinity level needed for balance. The alkalinity and calcium hardness levels needed should be within the recommended ranges. Alkalinity can be raised by adding sodium bicarbonate (baking soda) and lowered by adding muriatic acid or sodium bisulfate (dry acid). Calcium hardness can be raised by adding calcium chloride but can only be lowered by replacing part or all of the pool water with lower calcium hardness water.
Del. Admin. Code tit. 16, Department of Health and Social Services, Division of Public Health, Health Systems Protection (HSP), 4464, app B