Various body positions are possible for filling the colon.  None is correct or necessarily more effective than another.  Experiment and find the one you prefer.  Some fill their colon kneeling and bending forward in the bathtub or shower because there will likely be small dribbles of water leaking from around the nozzle.  Usually these leaks do not contain fecal matter.  Others prefer to use the bathroom floor.  For the bony, a little padding in the form of a folded towel under knees and elbows may make the process more comfortable.  You may kneel and bend over while placing your elbows or hands on the floor, reach behind yourself and insert the nozzle.  You may also lie on your back or on your side.  Some think the left side is preferable because the colon attaches to the rectum on the left side of the body, ascends up the left side of the abdomen to a line almost as high as the solar plexus, then transverses the body to the right side where it descends again on the right almost to the groin.  The small intestine attaches to the colon near its lower-right extremity.  In fact these are the correct names given for the parts of the colon:  Ascending, Descending and Transverse Colon along with the Sigmoid Colon or Rectum at the exit end.

As you become more expert at filling your colon with water you will begin to become aware of its location by the weight, pressure and sometimes temperature of the water you’re injecting.  You will come to know how much of the colon has been filled by feel.  You will also become aware of peristalsis as the water is evacuated vigorously and discover that sensations from a colon hard at work, though a bit uncomfortable, are not necessarily pain.

Insertion of the nozzle is sometimes eased with a little lubricant.  A bit of soap or Ky jelly is commonly used.  If the nozzle can be inserted without lubricant it will have less tendency to slip out.  However, do not tear or damage the anus by avoiding necessary lubrication.  After insertion, grip the clamp with one hand and open it.  The flow rate can be controlled with this clamp.  Keeping a hand on the clamp also prevents the nozzle from being expelled.

Water will begin flowing into the colon.  Your goal is to empty the entire bag into the colon before sensations of pressure or urgency to evacuate the water force you to remove the nozzle and head for the toilet.  Relaxation of mind and body helps achieve this.  You are very unlikely to achieve a half-gallon fill up on the first attempt.  If painful pressure is experienced try closing the clamp for a moment to allow the water to begin working its way around the obstacle.  Or, next time try hanging the bag lower, reducing its height above the body and thus lowering the water pressure.  Or, try opening the clamp only partially.  Or, try panting hard, so as to make the abdomen move rapidly in and out, sort of shaking the colon.  This last technique is particularly good to get the water past a blockage of intestinal gas.