Hi, just so I understand, the water isn't coming directly from the shower head into your colon is it? If it's a gravity flow type system, the water should first be directed into a container from where it flows by gravity into your colon. If it's not, then there is a risk of a sudden pressure surge forcing too much water into your colon too quickly that could have very dangerous consequences.
If it's a closed system, then the water would enter a unit with automatic pressure release controls that would automatically either shut off the flow, or bypass the inflow to your colon. This is a standard safety feature on all modern (after 1982) pressurized colon hydrotherapy systems.