Shredded Pork Sandwiches

Shredded Pork Sandwiches
1 Boneless pork shoulder roast (3-4 pounds)
1 ¼ cup ketchup
½ c water
½ c diced celery
¼ c diced onion
¼ c lemon juice
3 T vinegar
2 T Worcestershire sauce
¼ c b sugar
2 t ground mustard
1 t salt
1 t pepper
Hamburger Buns
Slow cook in slow cooker for 6 hours or until you can easily pull meat apart.