Barbecue Beef Sandwiches

I got this recipe from my friend Natalie. Its really yummy!

3 lb. roast
1 chopped onion
3 cups chopped celery
1 cup ketchup
1 cup good BBQ sauce
1 cup water
2 tbsp. white vinegar
2 tbsp. Worcestershire sauce
2 tsp. garlic
1 tsp. chili powder
1 tsp. salt
½ tsp. pepper

Cook in crockpot on high(I used the low setting on my crockpot because my High setting is too powerful) for 6-7 hours. Shred the beef and mix back in with sauce. Serve on buns.