Can one use a toilet plunger on shabbos if the only toilet in the houses backed up?
This is a very controversial issue. On one hand there are numerous poskim that prohibit it, but on the other hand there are poskim that say that if there is a very big need, that it may be done with a household plunger, (not with a professional one). Others say that it may be opened by a gentile, or in a backhanded way. Meaning that if it can be done with ones left hand or with only one hand then it would be permitted. If that can’t be done there are numerous poskim that one may rely on.
The issue here is that it may be Mileches Ssosair, – Demolishing, since the garbage that is stuffing the toilet is in a way attached to the toilet and therefore to the building. The Shulchan Aruch O:CH 336-9 says that a gutter pipe that got filled with leaves, and it is causing a leak in the house that the leaves may be stuffed down the pipe to unclog it with ones foot. The heter is based on the fact that the person is doing is being done in a backhanded manner therefore it is only a rabbinic prohibition, and permitted in order to prevent the damage. However when using a plunger it isn’t considered a backhanded manner and might be an Issur dorayso. Another issue would be that it is tikun mana- fixing the toilet, or uvdin dchol- a weekday like action because a special instrument is being used. For these reasons many poskim prohibit its use. See Tzitz Eliezer 7-12(7), Ohr L’tzion 2-27 (12), Mishne Halachos 6-81,82,83, Yabia Omer 5 O:CH 33, Chut Sani 2-pg. 243, Nishmas Shabbos Siman 337-252,253, Aliba D’hilcoso vol. 69 pg. 32, in the name of R’ S. Doblitsky and R’ Ezriel Auerbch shlit”a, Hilchos Shabbos B’shabbos 15-29, Orchos Shabbos 8-31 in the name of R’ Eliyashov zt”l. Minchas Yitzchok 5-75, 6-29, Vayaan Yosef 29, See Igros Moshe O:CH 4-40 (9) that if the toilet gets stuffed often then it would be permitted because it would be considered the norm and not considered “fixing”, otherwise it should not be fixed.
On the other hand R’ S. Z. Auerbach zt”l in Minchas Shlomo 2-13(3), R’ Vosner zt”l (M’bais Halevi6-pg. 45(11) and 19pg. 40 (12), Shulchan Halevi 9-7, and the Beer Moshe 1-29 permit using a plunger on Shabbos. Also see The Shabbos home pg. 420-422.