As a colon hydrotherapist, I can tell you that you are correct about enemas only clearing out the lower bowel, usually only to the sigmoid colon. Enemas are limited in their benefit and colonics are much more effective, however, enemas do not cause impactions. An enema uses the force of gravity so the pressure of the water would not be sufficient to push the fecal material back. Also, any water (should be purified or distilled) would help to hydrate the bowel and material contained within it so the material would pass more easily. colonics do this much more thoroughly, but enemas are a resonable and safe alternative if colonics are not available or desirable.