I know drinking water is a good way to flush the body, illness and helps weight loss. Is it good for post op surgery as well?

It is important to stay well hydrated in the post operative period but do not overdo fluid intake for  the first few days after surgery.    There may be some sluggishness of the bowel due to the surgery, anesthesia or pain medications that are narcotics based which can cause constipation leading to straining in stool evacuation. Because of the muscle tightening with a tummy tuck, straining is painful and restrictive. Drinking water will keep the stool moist and hopefully easier to evacuate. reducing the need to strain.   It does not  improve necessarily improve healing process.. 

Drinking extra water does not benefit your health and, when carried to an extreme, may cause health problems.  If you are not thirsty and your urine is not concentrated and dark, you are adequately hydrated.  All drinking more water does is make you run to the bathroom to pee.Drinking extra water after surgery does not speed healing.All the talk about extra water and losing weight, etc, is urban legend and has no scientific basis.