Eiruvin 8:7-8

Eiruvin 8:7

If a channel of water passes through a courtyard, the residents may not draw from it on Shabbos unless they constructed a partition ten handbreadths high (about 30”) where it enters and exits the courtyard. Rabbi Yehuda says that the courtyard wall that passes over the channel of water serves this purpose. As a support for his position, he cited an incident in a town called Aveil where the local authorities permitted residents to draw water from such a channel without special partitions. The Sages responded that this wasn’t because the courtyard walls took the place of the partitions, it was because this particular channel of water did not meet the minimum dimensions of four handbreadths wide by ten handbreadths deep (approximately 12” x 30”).

Eiruvin 8:8

If a balcony extends over a body of water, they may not draw water (through a hole in the balcony) on Shabbos unless they constructed a partition ten handbreadths high, whether on the top of the balcony or on its underside. The same is true in the case of two balconies, one above the other (that each one requires its own partition). If the residents of the upper balcony made a partition and those on the lower balcony did not, neither may draw water unless they make an eiruv together.