Crock Pot Barbecue Beef

1 (2 1/2 pound) chuck roast
1 cup water
1 bottle barbecue sauce
1/3 cup Worcestershire sauce
1 teaspoon mustard
1 onion, chopped
Salt and pepper

Add all ingredients to crock pot. Cook on HIGH heat until it boils. Simmer on LOW for 6 to 8 hours. Chop meat and stir all well. Serve.