Epsom Salt works by drawing water into the intestines. The Sea Salt water is the same specific gravity as human blood and ideally should flush through the entire digestive system without being absorbed into the blood stream.
If necessary you can take Epsom Salts during Master-Cleanse for a laxative. It can be pretty harsh and should not be done everyday. Not only do you risk getting dehydrated and messing up your electrolytes; Epsom Salts can leave you with a very sore backside. Just ask some of the regular liver flushers. (I'm one of them, and know first hand about the raw places)