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11. May one unplug a drainage pipe on Shabbos?
It is forbidden to unplug a stuffed drainage pipe on Shabbos unless lack of doing so will cause flooding to one’s house, in which case one may discreetly press on the blockage of the pipe with an irregularity. [It is However, forbidden to remove the items causing the blockage from the pipe.]
Example: If one’s rain pipes on his roof became stuffed with dirt and twigs and is causing flooding in one’s house, one may use his feet to press down the blockage, allowing the water to flow freely.
It is permitted to undo a blocked drain if all the conditions apply:
1. It will cause damage to one’s property.
2. One uses an irregularity to free the blockage, such as one steps on it with one’s feet.
3. One does not remove the blockage from the drain.
4. One does so discreetly.
May one unplug a stuffed toilet or sink?
Yes. One may even use a plunger or “snake” to do so. However, some Poskim limit this allowance to only if it is a common occurrence and if it is not completely stuffed. Others allow it without difference. If easily available it is best to do so through a gentile. If However, the blockage is so strong that it requires the work of a professional, then one may not do so on Shabbos, unless he fulfills all the conditions mentioned above.
 Admur 336:15; Michaber 336:9; Kesubos 60a
 Admur ibid and Michaber ibid rule it may only be done “Betzina” in discreet.
Other opinions: Some Poskim rule it may be done even in public if necessary. [Beis Yosef in name of Ran; See Biur Halacha 336:9 “Betzina”]
 As since this case involves loss, the Sages did not decree against fixing the pipes in an irregular way. [ibid]
 M”B 336:47
 Beir Moshe 1:29; Minchas Yitzchak 5:75; 7:19
The reason: As this is not a true blockage, as certainly some water goes through and it is very easy to open, as is seen that with a mere push of air the entire blockage is freed. It is thus not similar to the case in 336:15 where the drainpipe was blocked with twigs, as in that case the blockage formed a complete block. It is rather similar to 314:6 by the plug of a barrel of wine that is above the sediment, which is permitted to remove. In addition to all the above, by a toilet there is a lot more room to be lenient as it is a case of Kavod Habriyos, and thus one may be lenient just as the Sages were lenient in many matters of using the bathroom in chapter 312. [Beir Moshe ibid; Minchas Yitzchak ibid]
 Igros Moshe 4:40
 As only then is it not considered Tikkun Keli, as explained in 314:6 and 336:15; Seemingly the Igros Moshe does not accept the differentiations brought in the Beir Moshe and Minchas Yitzchak above.
 Bier Moshe and Minchas Yitzchak ibid
 Minchas Yitzchak 5:75; 7:19
 So is implied from Beir Moshe ibid; Minchas Yitzchak ibid as then it is exactly similar to the case