Powdered Alum is usually only available at large chemical supply companies and due to Homeland Security Regulations imposed on those companies, you must be a "registered Company" to purchase from them...that said, using a trash pump or sump pump in your barrel to recirculate the granules, breaking them up and disolving them much quicker....be sure to move the intake and outlet to mix thoroughly, The Alum slurry look like dirty milk.
You can buy both aluminum sulfate and potassium permanganate on Ebay. I've bought PP there with no questions asked.
