Knotting a Garbage Bag on Shabbos
Question: How may a garbage bag be tied on Shabbos or Yom Tov?
Discussion: One must be extremely careful about how garbage bags are tied on Shabbos and Yom Tov, since once a garbage bag is tied up, the knot is generally left as is until the bag is picked up by the garbage collectors days later. A knot left for that length of time may be considered a permanent knot, and tying it on Shabbos may be strictly prohibited.163 Thus, the common practice of bunching and twisting the top of the garbage bag, making a loop, pulling the ends of the bag through the loop and tightening the loop to form a knot is forbidden. It is also forbidden to extend the two top corners of the bag, tie them together and make a bow (as if tying a shoelace), or to tuck in the corners of the bag under the knot to strengthen the knot. The only permissible knots that could be made on a garbage bag are a slip knot — a loop which is not completely pulled through and does not form a knot at the top of the bag; or a single knot, which is like the first stage of tying a shoelace. Such knots can be tied with a bow or another knot on Motza’ei Shabbos.
An alternative solution for sealing garbage bags which totally avoids any forbidden Shabbos Labors is to use a rubber band instead of tying a knot. Rubber bands keep bags as tightly sealed as a knot or a twister.
163. See Tikunim u’Miluim 35, note 63 and Ayal Meshulash, Kosher u’Matir, pg. 136.