Trying to figure out this sign that I saw hanging in a Shul (picture attached) saying to let the water run after you fill your cup up and then turn the faucet off. Can you explain how this helps with using a filter on Shabbos?
Without getting into the actual halacha if you should do this or not, I can’t explain this to you, because I don’t understand it, and I don’t see the connection to what the Chazon Ish writes in ס’ נ”ג. Rav Vosner in שבט הלוי חי”א ס’ צ”א-ב writes that the opposite should be done, let the water run first for a few seconds and then put your cup under the faucet. Don’t rely on this for halacha l’maaseh, I am only commenting on your request to explain the sign.
Have a good Shabbos