Is there not here... ?. similar question asked before by Jehoshaphat (1 Kings 22:7).
poured water, &c. Put by Figure of speech Metonymy (of Adjunct), App-6, for being an attendant.
Related Commentaries of 2 Kings 3:11
2 Kings 3:11
11 But Jehoshaphat said, Is there not here a prophet of the LORD, that we may enquire of the LORD by him? And one of the king of Israel's servants answered and said, Here is Elisha the son of Shaphat, which poured water on the hands of Elijah.