Oooops!...I knew I left something out...thanks for asking your question.
With either system, it is possible for the colon hydrotherapist...and sometimes the client, depending on how the system is set up....to see what is being expelled from the client. In the closed-system there is a portion of the outflow hose that is clear tubing enabling the waste to be viewed before it enters the general plumbing system. In the open-system, once the waste enters the drain below the client it goes through a series of tubing...one which is a view tube...and then enters into the plumbing system. Some colonic machines are also able to retrieve samples that can be sent for lab analysis (doctors order is required for this service).