I just posted some of this elsewhere:
Some time ago, I was in hospital and got very constipated because of some meds. I felt really uncomfortable and my rectum felt badly packed. In fact, it got to the point I could not pee more than a bit and had to be catheterized, which was not fun. The nurse had a difficult time getting the Fr 16 Foley catheter into me because the poo in my bowel was pinching the urethra. So effectively, the constipation was causing an inability to pee. But I digress.
I was peeing lots through the catheter and I finally convinced the doctors to order a plain water bag enema. A bit later the nurse came in with a disposable kit, I think it was an MDI:
https://www.expressmed.com/mckesson-microtek-medical-center-hang-enema-bag-1500-cc-touchnseal-valve-latexfree-50800.html
Anyway, the nurse filled it with water and hung it, inserted the nozzle and started the flow. The water was pleasantly warm and she continued to advance the tube as the water flowed. The tube probably went in about two feet and the water flowed the whole time, causing little cramping. The results were dramatic with a very strong urge and lots of poo for perhaps a half hour.
My point is that you can give or get very large, high, and extremely effective enemas with just warm water in a disposable bag. The disposables have tubing which is about Fr 24 and are plenty stiff to get fully up someone. It is quite possible that the Foley helped with the enema because my bladder was completely empty before, during, and after the enema.