Diluted Wine for Kiddush
A. Regarding dilution of wine with water, Shulchan Aruch (Orach Chaim 204:5) writes that we must assess each wine based on the common practice in each location for how much is usually added. The Mechaber 204:5 tells us that our wines today are not considered strong. It therefore stands to reason that since the wines that we drink today are never diluted with water, since they are not strong, one should add only a minimal amount of water. This is permitted since it does not change the taste of the wine, but one should not add an amount of water to the wine or grape juice that will alter their taste. Sefer Madnei Shlomo (pg. 52) quotes in the name of Rav Shlomo Zalman Auerbach zt"l that one should not add more than 1/3 water to grape juice, because this would significantly change the taste. Some have a minhag to add a few drops of water to their Kiddush wine which is permitted based on the above.
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