Not sure what you mean by "water therapy". If you mean a high volume enema, this is not a medically justified procedure. It is not necessary to "detox" the colon. This is a myth promoted by people who want you to pay them for snake oil treatments.

Water is a great cleanser, although not all water is equal. If you do not trust your local water supply, you need to get bottled water. 3-4 liters per day should clean out your system well.

Are you referring to water fasting?
If yes, 5 day water fasts are used often in functional detoxification plans. A water fast can reduce inflammation, stimulate cellular cleansing called autophagy and produce stem cells to regenerate new tissue., as well as jump start a weight loss program. There are also fasting mimic diets, such the Prolon Diet, which is 5-day meal program providing scientifically researched micro- and macro-nutrients in precise quantities and combinations that nourish you, but are not recognized as food by your body and therefore mimics a fasting state! It is considered the health trend of fasting without going hungry! www.tinadiscepolamd.gethealthy,store.com

Water is used to make enemas that can cleanse the lower parts of the colon.