The Alum I put in lowered the pH to 7.4 (I tested when the water was still cloudy white) but it went back up to 7.8 when full mixed in after 8 hours.
Hydrated lime is part of the total Alum reaction treatment. It adds extra positively charged ions and starts the process faster than Alum alone. I rarely apply under 200 pounds alum per acre foot of water.
The jar test gives you a dosing rate only if you have very precise scales and volumes to start with....plus, it is a reaction in a small, undisturbed setting...hardly close to real world application conditions.
