Rif Eruvin 29a {Eruvin 87a continues ... 88a}

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29a

{Eruvin 87a continues}
Rabbi Yehudah says: A wall over it may be regarded as a partition.
Rabbi Yehudah said: It happened with the water channel of Abel that they would fill from it on the Shabbat on the authority of the elders.
They said to him: Because it was not of the prescribed size.

Gemara:
The Sages learnt {in a brayta}: If they made a partition at its entrance but did not make it a partition at its exit; or at its exit but not at its entrance; they may not fill from it unless they made for it a partition of ten handbreadths at its entrance and its exit. Rabbi Yehudah says: A wall over it may be regarded as a partition. Rabbi Yehudah said: It happened with the water channel of Abel which brought water from Abel to Tzippori that they would fill from it on the Shabbat. They said to him: Is this a proof? Perhaps it was not 10 handbreadths deep and 4 handbreadths wide.
To explain: The partition of a water channel needs to descend into the water channel such that it divides between the water in the public domain and the water in the private domain, just as the partition of the cistern which needs to descend into it in order to divide between his domain and his fellow's domain.

{Eruvin 87b}
Mishna:
If a balcony is above the water, they may not draw from it on the Shabbat, unless they made for it a partition ten handbreadths high, whether above, whether below.
So also, two balconies, this one above this one, if they made {a partition} for the upper and did not make for the lower – both are prohibited until they make an eruv.

{Eruvin 88a}
Gemara:
Rabbi Abba cited Rav Huna {our gemara: Rabba bar Rav Huna said}: Do not say that specifically filling up is permitted {with a suspended partition present} but to pour out {into the water channel} is forbidden; rather, even to pour is also permitted.
Rav Shizvi said: This is obvious! For this is identical to the case of a trough!
I might have said that there {by the trough} the water is absorbed {into the ground} whereas here the water is not absorbed {but flows with the rest of the water out of the domain, and so it should be forbidden}. Therefore it informs us {that it is permitted}.

"So also, two balconies...":
Rav Huna said {our gemara: citing Rav}: They only taught this in the case where it {the lower balcony} was near it {the upper one}, but if it was distant from it {four handbreadths}, {with a partition} 10 handbreadths high, the upper one is permitted.

Mishna:
If a courtyard is less that four cubits, one may not pour out water into it on Shabbat, unless they made for it a pit holding two se'ehs from the hole downwards, whether on the outside or on the inside.
However, on the outside he must cover it; on the inside he need not cover it.