Komentarz do Rodzaju 24:19

עד אם כלו literally, UNTIL THAT THEY HAVE FINISHED [DRINKING] — Here the word אם is used in the sense of אשר “that”. The words אם כלו the Targum renders by "That they have done enough drinking”. Though the verb כלה signifies to finish, to end, the Targum is right in translating it thus for this is the end of their drinking when they have drunk as much as they wanted (cf. Rashi on Genesis 43:2).

ותכל להשקותו ותאמר, she waited with speaking until Eliezer had finished drinking his fill. She followed the dictum of our sages that one should not engage in conversation while eating (during the meal) (Taanit 5)

ותכל להשקותו, When she completed giving him to drink, etc. Seeing that the Torah does not describe Eliezer as having finished drinking, it is clear the Torah wants us to know that she kept bringing him water until he stopped drinking.