Pour three quarts (12 cups) of cold filtered water in a large container.
Warm up ground coffee in the microwave for 15-30 seconds to get the oils warmed up and the flavors to release. Add 1 1/2 cups of ground coffee beans to water. Stir to combine coffee grounds.
Cover container. Let steep at room temperature for at least 12 hours and up to 24 hours.
Line strainer with coffee filters and place over large container.
Slowly pour coffee into prepared strainer-filter. The coffee will pass at a slow stream. If desired, change coffee filters as necessary. Discard coffee grounds. Transfer cold brewed coffee to a pitcher and keep chilled in the fridge until ready to use. This coffee is a little concentrated, so I don’t suggest just drinking it pure unless you like STRONG coffee.