Spray inside of 5- to 6-quart slow cooker with cooking spray. Cut ribs into 2- or 3-rib portions. Place ribs in cooker. Sprinkle with salt and pepper. Pour water into cooker.
Cover and cook on Low heat setting 6 to 7 hours. Remove ribs from cooker; place in shallow baking pan. Drain and discard liquid from cooker.
Brush both sides of ribs with barbecue sauce. Return ribs to cooker. Pour any remaining sauce over ribs. Cover and cook on Low heat setting about 1 hour or until ribs are glazed and sauce is desired consistency.