Over the years there have been a variety of colonic irrigation "machines." Some are pretty interesting and some are downright scary!
My first encounter was with a Coombs machine.... it seems like the only thing missing was the traveling spark gap from science fiction movies! A huge wall mounted device with a roll around cart with the viewing tube. This machine in particular is/was a health risk. While the nozzles may have been cleaned, the tubing and the viewing tube could be a real source of contamination.
In the 1980's I visited a therapist in Hamtramck, MI near Detroit. I had been there several times, and on one occasion I could get a fill but no release, and after some investigation the therapist realized the outflow tube was plugged from the previous client. While the therapist messed with the tube I went to the toilet to release. I was NOT happy! Her suggestion when I got back was a series of enemas, and since she used E-Z-EM disposable bags that was agreeable. From that time on I never had another colonic there, but returned many times for a series of enemas.
That clinic was also interesting, on your first you were given a barium enema x-ray, just one shot, so the chiropractor that owned the clinic could recommend a "treatment."
I've experienced 3 Coombs machines in Los Angeles, Detroit and Pittsburgh. I wonder it there are any still out there?
Also from that period was the Dierker Machine, I bought one on eBay a few years ago, they are unique in that they have negative pressure (slight vacuum) on release, and make a lot of noise! I've equipped the one I have for disposables and replaced the manometer tubes that contained mercury with gauges. Last one I saw was in a therapists office was in Dallas about 30 years ago, same question, any still out there?
Now most of the closed machines are of a similar design, with temperature controls, pressure gauges and viewing tubes... and disposables.
Some of the more interesting machines are the gravity feeds, my first colonic with one of those was in Boston, which was a big stainless steel tank on the wall, some large diameter tubing connected to valves and a nozzle. The only downside was the viewing tube, only the therapist could see it. With no pressure gauge the therapist would be estimating how much water you had taken, and if you hadn't taken enough in her opinion, you got a lot of encouragement to take more. I've only had this happen one or twice, but on one visit I just couldn't take much water. So the therapist suggested I get off the machine for a series of enemas!
Same problem, so a colon tube was suggested, and after a couple of tries and at last a very deep insertion things unlocked. OK, from then on I alternated sessions with colonics and enemas, and opted for a lot more enemas.