How Does Rezum Water Vapor Therapy Work? Rezum Water Vapor Therapy is a non-surgical treatment that uses the natural energy stored in water vapor, or steam, to remove excess prostate tissue that is pressing on the urethra. Rezum Therapy is typically performed right in your urologist’s office, or at an outpatient surgery facility and completed in one short appointment. During each 9-second treatment, sterile water vapor is released throughout the targeted prostate tissue. When the steam contacts the prostate tissue, all the stored energy is released into the tissue. Your doctor will determine the amount of treatments you need, based on the size of your prostate. Over time, your body’s natural healing response absorbs the treated tissue, shrinking the prostate. With the extra tissue removed, the urethra opens, reducing BPH symptoms.