Dhauti is a method for cleansing the entire gastrointestinal (GI) tract. It entails drinking two quarts or liters of salted water (two teaspoons of salt per quart or liter) slowly but steadily glass by glass over about 15 minutes. Then lie down on the left side (for best flow through intestines) for 20 minutes. Then go to the toilet, if the urge has not sent you there already. The salt prevents immediate digestion, and the water passes through the entire digestive tract, flushing everything in the digestive system out with it.
Dhauti, which is a shatkarma technique, should not be done often, as it depletes the system of natural biochemicals.