720. A Pit to Collect Water

Shabbos 15:16

We may not pour water into a courtyard that is smaller than four cubits by four cubits (about 6’x6’) on Shabbos because the water will quickly reach the public domain. In such a case, one must dig a pit two seah in volume (about seven gallons) in the courtyard or in the public domain adjacent to the courtyard, for the water to collect. A pit in the public domain must be covered from the outside so that it will not be visible from the public domain. A courtyard and its patio are combined to form the area of four cubits. A pit that holds two seah would be half a cubit by a half a cubit (about 9”x9") and 3/5 of a cubit deep (about 11”).

[Editor’s note: a hole of this size would only hold about four gallons, not seven. We provide ballpark estimates of measures for handbreadths, cubits, etc. so that users will have an approximation of whether we’re talking about inches, feet, miles, etc. but there are different opinions as to these measures. In this instance, our approximation for units of length and for units of volume do not happen to line up.]

Shabbos 15:17

If the pit cannot hold two seah, we may only pour its actual volume into it. If it can hold two seah, any amount of water may be poured into it, even if it will overflow the pit. This applies in the rainy season, when courtyards are muddy and drainpipes are flowing with water so passersby will not say that the person is causing the water to flow into the courtyard. In the summer, however, if a pit can hold two seah, then only two seah may be poured into it, and if it holds less, no water may be poured into it at all.