I have posted something about this subject because I do prefer to take my enemas with a colon tube. My very first enema was given to me with a colon tube in a hospital when I was four years old - which I have also posted about. And I have also said previously that those of us who administer with a colon tube are the minority.
However, regarding the technique for inserting a colon tube deeply high up in to the colon depends on several factors, many of which other members have already mentioned in the various posts and blogs on Zity. Thus, it is sufficient to say that what works well for one individual, may not work as well for another. You must experiment on your own body until you discover what works best for your body. But I will say that enemas are one of those few things in life that are more enjoyable when done with a partner and also produce better results. Unfortunately, I have no choice but to administer mine solo.
So, based on my personal experience (50 years give/take), the French size and the stiffness/ rigidity (flexibility) of the colon tube is the first factor you must consider. The different Fr sizes will impact on flexibility, as well as the composition of the rubber itself. Some rubbers are softer than others. I have noticed by way of personal experience that the colon tubes commonly available on eBay and Amazon are stiffer than those used on me in the hospital when I was a younger. In addition to several new ones, I am lucky to still have a 20-inch 30Fr that I purchased more than ten years ago from a German company that no longer retails. Also, the older ones were not limited to a maximum of 20-inches. Yes, I did hours of research on the availability of longer colon tubes, and there is a company operating out of Europe that will sell medical equipment including colon tubes that are 150 cm long, though they are not listed as a colon tube. However, most manufacturers that supply longer that 20-inches for under US$5 are based in India, but they expect you to order a minimum of 400/500 units before they sell anything. Amazon and eBay (who possibly purchase their stock from those same Indian manufactures) know this, that is why they can charge you US$25+postage for only a 20-inch. If you want to learn something on length and flexibility of the older colon tubes feel free to watch a related video that I discovered in another person’s post https://biguz.net/watch.php?id=2033906&name=jake%27s-colon-tube-enema.
Another factor to consider is the size and shape of the colon itself base on the age and body size and shape of the individual. A pre-teenager will have narrower colon than an adult as will a slimmer torso compared to a thicker torso. I remember from the enemas that I received in hospital between 4–8-year-old, that whenever the colon tube was inserted by the nurses, it would effortlessly penetrate my anus and snake its way deep high up into my colon without bumping or catching against any of the nooks and crannies. However, whilst I self-administrating my enemas, I can feel my 30Fr 20-inch colon tube tip bumping against the back rectal wall and exerting some noticeable pressure. At this point, before it push further, I must allow some water to flow into my rectum to expand it open enough to allow the colon tube tip to find the opening between my rectum and sigmoid section so it can continue onward in its journey through the sigmoid. And, even after overcoming this hurdle, I often feel the colon tube tip bumping into the left side of my lower abdomen before it turns upward into my descending colon section. The only exception to this that I have noticed is when faecal matter is already present in my sigmoid-rectum sections, at which time the colon tube tip seems to effortless snake its way up without any bumping and snagging. This is obviously due to the faecal matter propping open the passageway – hence no need to pre-inject any water.
As I have stated above, you have to experiment with your own body until you find what works best for you. All the best and be safe!