Rinse clams under cold running water
Discard any cracked, broken, or open clams that do not close when tapped
Place clams in a large bowl or bucket
Cover with cold saltwater made from 1/3 cup salt per 1 gallon water, or use clean seawater
Keep clams submerged lightly, with room for them to breathe
Let them sit in a cool, dark place for 20 to 60 minutes
Drain and discard the dirty water
Refill with fresh cold saltwater
Repeat until no sand remains in the water, usually 2 to 3 times
Scrub the shells lightly if needed
Rinse clams well before cooking
Keep purged clams refrigerated until use