According to your other post, you only took one teaspoon at a time --- not nearly enough to do much as far as a laxative effect.
There is a tolerance level when you start taking Epsom Salts by the tablespoon. Most people in their initial flushes have never done much colon cleansing and the magnesium from the ES will get things moving after the first tablespoon. If you're already somewhat cleaned out, it will probably be sometime after you take the 2nd tablespoon.
As far as hydration goes, make sure you are well hydrated before attempting a liver flush.