Pour cold water and ground coffee into a large bowl and mix until all coffee is completely wet. Cover and set in the fridge for at least 12 hours and up to 24 hours maximum.

Remove the bowl from the fridge and strain your coffee "concentrate" into another large bowl through a coffee filter or cheese cloth lined mesh mesh sieve. Once all liquid is separated, discard coffee grinds.

Sere coffee over ice and dilute with a 1:1 or 1:2 ratio of coffee to water depending how strong or weak you like your coffee.

Keep the remaining concentrate refrigerated in an airtight container for up to 1 week.