Season pork with salt and pepper, then place in the slow cooker. In a separate bowl, combine water, vinegar, Worcestershire sauce, and chili powder. Pour over pork.
Cook on low 8-10 hours, or on high 4-5 hours.
Remove the cooked pork to a cutting board, and discard the cooking liquid. Using two forks, shred the pork, and place back into the bowl of the slow cooker.
Add barbecue sauce to the pork and stir to distribute. Place slow cooker on high, and cook for 30 minutes. Serve on Kaiser buns, or as desired.