I got one of the silicone double balloon nozzles for Christmas two years ago. (Do I have a good hubby, or what?) This unit has the interior balloon extra large; I think it's 500cc. To put that in perspective, a soda can is 355cc. It is simply a wonderful klismo toy, and it does do a great job with retention.
I put an additional clamp on the neck of it, outside of both bulbs, so I can remove the noz entirely from the enema bag tubing and walk around with just the enema and noz in me. It is just so remarkably kinky having these two black rubber inflator bulbs attached to me down there. I just cannot overlook that they have a very symbolic appearance of testicles! So with the enema inside me and my big black balls tucked into my undies or usually a girdle of some sort to help with retention, I'm free to walk about the house. I never fail to admire my pseudo-preggie look, and I usually spend time online enjoying enema sites. .
There was a small panicky learning curve. The additional clamp that I put on closes not just the large tube the water flows through, but it also closes off the air tubes to the two balloons. So the first time I used it, I tightened the clamp, disconnected, and after enjoying the sensations a while I sat down to let it out. I then unscrewed the valves on the inflator bulbs, and expected the air to rush out and deflate the balloons. But my clamp prevented the air from getting out! It took a bit of a thinking-through, which is hard to do while enduring intensely delicious colonic contractions that hurt so good.
I confess to a moment of panic, imagining myself permanently sealed tight down there while two quarts of water were inducing a stretched feeling of unpleasantness. I calmed myself down and logiced it out. Once I opened the additional clamp the noz deflated and was easily expelled, and all was well. So, yes, minus operator error the double balloon catheter does get my vote of confidence as a retention device par excellence.
I have tried smooth silicone butt plugs, but they don't do a very good job with retention in my opinion, because they are free to move inward enough to let water leak past. It is surprising, though, how much of a retention aid a simple super-plus tampon can be. The bigger the better. No, you can't push against it hard like you can with the double-balloon, but if you exercise retention discipline the tampon will greatly assist.
Hugs,
Diane