אורח חיים שנ״אOrach Chayim 351

Se’if 1א׳

לֹא יַעֲמֹד אָדָם בִּרְשׁוּת הָרַבִּים וִיחַבֵּר יָדוֹ לְמַזְחֵלָה, שֶׁהוּא צִנּוֹר אָרֹךְ מֻנָּח לְאֹרֶךְ הַגַּג, בְּתוֹךְ ג' טְפָחִים סָמוּךְ לַגַּג וּלְקַבֵּל הַמַּיִם מִמֶּנָּה שֶׁכֵּיוָן שֶׁהוּא בְּתוֹךְ ג' סָמוּךְ לַגַּג חָשׁוּב כְּגַג וְאָסוּר, בֵּין אִם הוּא לְמַעְלָה מֵעֲשָׂרָה אוֹ לְמַטָּה מֵעֲשָׂרָה; אֲבָל מֻתָּר לִקְלֹט מִן הָאֲוִיר אֲפִלּוּ אִם יָדוֹ תּוֹךְ ג' לַמַּזְחֵלָה. הָיְתָה מַזְחֵלָה בּוֹלֶטֶת ג' מִן הַגַּג, וְכֵן סְתָם צִנּוֹר שֶׁבּוֹלֵט ג', יָכוֹל לְחַבֵּר יָדוֹ אֲלֵיהֶם וּלְקַבֵּל הַמַּיִם, וּכְגוֹן שֶׁאֵין בָּהֶן ד' עַל ד' וְהֵן לְמַטָּה מֵעֲשָׂרָה; אֲבָל אִם יֵשׁ בָּהֶן ד' עַל ד', אוֹ אֲפִלּוּ אֵין בָּהֶם ד' עַל ד', וְהֵן לְמַעְלָה מֵעֲשָׂרָה, אָסוּר.

The Law of One Who Reaches Into a Pipe in the Public Domain to Drink: A person should not stand in the public domain and put his hands up to the gutter, which is a long pipe that is attached parallel to the roof and is three tefachim from the roof, to take water from it. Because it is three tefachim from the roof, it is considered like the roof and this is forbidden whether it is above ten tefachim from the ground or below. However, one is permitted to collect water from the air, even if his hand is within three tefachim of the gutter. If the gutter is three away from the roof, and same is true for a generic pipe that is three away, one may put his hands on them to collect water. This is if they are not four by four tefachim and they are below ten tefachim from the ground, but if they are four by four, or even if they are not four by four but are above ten, this is forbidden.