Every treatment is individual, but as a guide we estimate around 60 litres of filtered water is used per treatment. However, only small amounts of water are allowed to enter the bowel at any one time. The water acts as a stimulant to tell the bowel it is full, and the bowel muscle responds by contracting and eliminating waste matter and the water.
It acts in the same way as when your bowel is full normally and you have the feeling you want to go to the toilet.
The water pressure is carefully controlled and is in fact lower than is normally generated during a bowel movement.