Has anybody tried hanging your enema bag from a bungee cord. If you find the right spring rate bungee cord the enema bag will raise as it empties. This makes the enema pressure increase as you get more enema water into you. I find having the enema bag raise by the height of the bag, as it empties, works best. (basically keeping the top of the water, in the enema bag, at the same level) The more enema water your bowel has in it, the more it is stretched and the more pressure it takes to keep the water flowing in. Raising the bag as it empties increases the pressure and keeps the flow, of the enema water, into you constant. Using a rigid wall container (enema can or bucket) makes the flow rate even more constant.
This system works well for solo enemas. It is a pain in the neck (I would normally say, "Pain in the ass" but the pain in you ass is either coming from the enema or is why you are taking the enema) having to get up, in the middle of the enema, and raise the bag to keep the enema flowing in to you.
My first method of solving this problem was to hang the enema bag from a cord that passed through a pulley and was tied off within reach of where you will be laying during the enema. That way you could raise the enema bag without getting up. The pulley system also is nice because you raise the enema bag momentarily for a short burst of pressure or flow.