The small intestine is where most of the food is digested and processed. The large colon mostly absorbs water and minerals. The large colon is about 40 inches long and is in an upside U shape around the edges of the abdomen. A rubber tube about 20-30 inches long is inserted. Up to 20 gallons of warm water is run through the tube, a few pints at a time, and cascades down the colon.
Some alternative therapists use coffee, herbs, extracts, or enzymes in the solution.
In stark contrast, an enema uses a tube a few inches long and about a quart of water. The medical profession refers to this procedure as colonic irrigation. When the colon has to be examined it must be empty. Still, full emptying is often obtained by a short course of fasting and laxatives. This is uncommon.