Experience dictates a cautious approach,
starting with an initial dose of
10 mg/L alum (27 pounds of alum per
acre-foot of water) followed by additional
applications in 5- to 10-mg/L
increments as needed. Alum should not
be used in waters with total alkalinities
of less than 20 mg/L as CaCO3 because
even small amounts may reduce pH to
dangerous levels.