@eboyhou
With regard to the machine v. Woods systems:
First a bit of a tutorial: A water source has two variables: the pressure and the flow.
Pressure is the amount of force per unit area. Flow is the volume of water that flows out per second.
Water, or any fluid, requires a pressure difference to flow and the flow is ALWAYS from high to low. No pressure difference, no flow.
In a Woods type system, the pressure is provided by the difference in height between the top surface of the water in the reservoir and the recipient's anus. This is exactly the same as the pressure from a bag enema. So, the recipient feels the gentle pressure of the water, gently urging it's way into and upwards in their colon. If there is resistance ('back pressure') the flow stops and only continues when the back pressure relaxes. So the recipient's colon fills at a rate that is comfortable. The disadvantage of this system is, if the recipient gets a cramp, water, soiled with poo, can be forced backwards into the reservoir. This is especially visible when the conical glass reservoirs from a Dierker machine are used. When watching such a tank, several decades ago, I cramped badly and saw a cloud of brown water appear in the tank. That was the last time I ever went onto a Woods machine. Perhaps check (one-way) valves are now built into such machines, but I'd want to be very, very sure.
The Dotolo type machines (most all) are constant flow, which means that the water flows at a constant rate, no matter what the back pressure from you colon is. Operation depends on the therapist… if they see the pressure going too high, the fill/release valve is opened and the water dumped.
There are a very few machines that are ‘dual mode’… constant pressure and constant flow… but I've never been on one.
IMO, the constant pressure machines give a much more comfortable colonic session, but have safety concerns.