Place pork chops in bottom of slow cooker. Top with onions.
In a bowl, mix ketchup, brown sugar, chili powder and water together. Spoon sauce over all. (If the chops need to be stacked in order to fit into your cooker, make sure to top each one with sauce.)
Cover and cook on High 3–4 hours, or on Low for up to 6–7 hours, or until meat is tender but no