I will preface by stating that I do not recommend this...it is possible to perforate the colon wall that could result in life-threatening complications. A colonic will accomplish this without the dangers as the quantity of the water itself reaches the entire length of the colon. It would be much safer to give yourself multiple enemas and have an occasional colonic to cleanse the entire colon.
That being said, colon tubes are used in the way that you describe...click on the link below for information about their use and a place to order them from: