אורח חיים ק״סOrach Chayim 160

Se’if 1א׳

מַיִם שֶׁנִּשְׁתַּנּוּ מַרְאֵיהֶן בֵּין מֵחֲמַת עַצְמָן, בֵּין מֵחֲמַת דָּבָר שֶׁנָּפַל לְתוֹכָן, בֵּין מֵחֲמַת מְקוֹמָם, פְּסוּלִים.

Which water is kosher or not for washing your hands with: Water that has had it's appearance changed doesn't work to wash your hands with, whether from itself or from something that fell into it or from it's location.

Se’if 2ב׳

עָשָׂה בַּמַּיִם מְלָאכָה אוֹ שֶׁשָּׁרָה בָּהֶם פִּתּוֹ, אֲפִלּוּ נִתְכַּוֵּן לִשְׁרוֹת בִּכְלִי זֶה וְנָפַל לַשֵּׁנִי, פְּסוּלִים; וְאִם צִנֵּן יַיִן בַּמַּיִם, פְּסוּלִים; וְאִם הֵדִיחַ בָּהֶם כֵּלִים, פְּסוּלִים; וְאִם הָיוּ כֵּלִים מוּדָחִים אוֹ חֲדָשִׁים, כְּשֵׁרִים. וְאִם הִטְבִּיל בָּהֶם הַנַּחְתּוֹם הַגְּלוּסְקִין (פי' כִּכְּרוֹת לֶחֶם), פְּסוּלִים, אֲבָל אִם טָבַל יָדָיו בְּמַיִם וְטָח פְּנֵי הַגְּלוּסְקִין, אוֹ שֶׁחָפַן מֵהֶם בְּחָפְנָיו, הַמַּיִם הַנִּשְׁאָרִים לֹא נַעֲשָׂה בָּהֶם מְלָאכָה, לְפִיכָךְ כְּשֵׁרִים אִם לֹא נִשְׁתַּנָּה מַרְאֵיהֶן. וְהוּא הַדִּין מַיִם שֶׁהַנַּחְתּוֹם מֵדִיחַ יָדָיו בָּהֶם מִן הַבָּצֵק הַדָּבוּק בְּיָדָיו (בֵּית יוֹסֵף בְּשֵׁם ר' יְרוּחָם).

If you did work with the water or soaked bread in it (even if you intended to soak your bread in one vessel of water and it fell into a second), that water is pusul for washing. If you cool wine in water, the water is pusul. If you wash vessels with water, that water is pusul (unless the vessels were already washed or new). If you dunk bread loaves into water, that water is pusul. But if you dunk your hands into water and smear it on the surface of bread or cup a handful of water and put that on, the water that is left in the jug hasn't "done work" and is kosher still as long as it's appearance hasn't changed. Rama: So too water that the baker rinsed his hands in to get off dough stuck to them.

Se’if 3ג׳

מַיִם שֶׁלִּפְנֵי הַנַּפָּח, אַף עַל פִּי שֶׁלֹּא נִשְׁתַּנּוּ מַרְאֵיהֶם, פְּסוּלִים, מִפְּנֵי שֶׁבְּיָדוּעַ שֶׁנַּעֲשָׂה בָּהֶם מְלָאכָה, דְּהַיְנוּ שֶׁכִּבָּה בָּהֶם הַבַּרְזֶל; וְשֶׁלִּפְנֵי הַסַפָּר, אִם נִשְׁתַּנּוּ מַרְאֵיהֶם, פְּסוּלִים; וְאִם לָאו, כְּשֵׁרִים.

Water that is in front of a blacksmith is pusul even if it hasn't changed in appearance, because it's known that he does work with it (that is, he cools metal with it). Water in front of a barber is pusul if it's appearance changed but kosher if it has not.