Cloudy water is a common situation for even the best cared for swimming pools, but the causes are not necessarily as common. Below is a list of scenarios that can lead to cloudy water. It's important to identify the cause of your cloudy water so that you can prevent it from coming back. Although water clarifier might be part of the solution, by itself it will not keep your pool from getting cloudy water again.
Possible Causes for Cloudy Water...
Low Chlorine
Algae Present (even though it might be dead)
High Combined Chlorine (Chloramines)
Tear/Rip/Hole/ in DE filter grid/element
Broken Filter
Undersized Filter
High Ph, Total Alkalinity, and/or Calcium Hardness
Identify and correct the cause of your cloudy water, Then.. Add 1 oz. per 5000 gallons of 
Let your filter system operate continuously for 48 hours. By this point, your water should be clear.
