Under what circumstances doe’s custom override halchah? Why do we say that custom is more important than law? If the halacha says we shouldn’t say a blessing on water then why do we? What is the importance of not breaking tradition in Jewish law?
1. This is a long and complex issue, in general if a practiced custom has a valid authentic source even if it halachacly challenged by the classic Poskim – one can follow the custom. (See Shaarim Hametzuyanim Bahalacha 2 p. 196; Minhagei Yisrael 1, p. 20 - 38) 2. A custom is not more important than a law, in some extreme cases it overrides as mentioned above. 3. Halacha says we do say a blessing on water. (Shulchan Aruch OC 204, 7) 4. Judaism is about tradition, breaking the tradition might lead towards abandon of Torah all together. Unfortunately we have experienced this in our past more than once.