The last that i heard, the official position by the Agriculture Extension folks in Louisiana is that it is bad touse salt to purge crawfish. Dunno exactly why and don;t want to argue the point, but not as many people do it as in the past. If the crawfish are really dirty, then hosing them off in the sack and then soaking them once or twice in clean water for a while seems to do the trick. If they are clean, then one soaking should do it. Of course, if you are really Jonesing for mudbugs, then you may just hose them off, then straight to the pot.