My father you well know, is organizing a very large Pesach Seder for our large family together. I have a number of questions that if permitted would make the Seder easier to prepare.
1) Since we need a large amount of wine for the four cups of our large group. How much can one dilute the wine with water and still comply?
A. Regarding dilution of wine with water, Shulchan Aruch (Orach Chaim 204: 5) rules that one must assess each wine based on the common practice of each location for how much is commonly added.
The Mechaber (ibid.) rules that our wines today are not considered strong. It therefore is reasonable that since the wines which we drink today are never diluted with water, and are nevertheless not strong, one should add only a minimal amount of water.
This is permitted when it does not change the taste of the wine; one should not add an amount of water to the wine or grape juice that will alter recognizably their taste. (Madanei Shlomo (pg. 52) quotes in the name of Rav Shlomo Zalman Auerbach zt"l).
Some have a minhag to constantly add a few drops of water to their Kiddush wine which is permitted based on the above.
Rabbi A. Bartfeld as revised by Horav Yaakov Hirschman, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.