Rinse the crawfish in a large container with cool water
Sort out any dead, cracked, or damaged crawfish and discard them
Fill the container with enough cool, clean water to cover the crawfish
Add salt if desired, using about 1/4 cup per 5 gallons of water
Let the crawfish soak for 15 to 30 minutes
Stir the crawfish gently once or twice during soaking
Drain the dirty water completely
Refill with fresh cool water and repeat the soak
Continue changing the water until it stays mostly clear
Stop purging when the crawfish look clean and active
Keep the crawfish cool and shaded until cooking
Rinse one final time before boiling or steaming