Put chicken breasts, potatoes, celery, and carrots in the slow cooker.
Mix the soup with water, salt, and black pepper. Pour over the chicken and vegetables.
Cook on low for 6-7 hours or high for 4-5 hours.
After cooking, stir to mix and break apart the chicken. You can also remove the chicken from the slow cooker and use forks to shred it, then put it back in the slow cooker. You want the chicken and the vegetables to be tender.
Mix Bisquick and milk in a small bowl to make the biscuit dough. Use a cookie scoop or large teaspon to make dumplings.
Drop the dumplings on top of the chicken mixture and push them down slightly to submerge in the mixture. Put the lid back on the crock pot and cook on high for 30 to 60 minutes or until the dumplings are cooked through. Do not stir the chicken and dumplings once you have dropped the dumplings on top!