Gemara

Rav Safra was in the Beis ha'Kisei. R. Aba snorted (to see if anyone was inside). Rav Safra told him to enter.

Berachos 26a (Mishnah): (To say Shma,) one must distance himself four Amos from urine and excrement.

(Rava): This suffices only if it is in back of him. If it is in front of him, he must distance himself as far as he can see.

The same applies to prayer.

Question: Rav Chisda permits praying while facing a Beis ha'Kisei!

Answer #1: That is when there is no excrement inside.

Objection: Rav Yosef taught that (the Isur to pray near) a Beis ha'Kisei is even if there is no excrement inside!

Answer #2: Rather, Rav Chisda permits praying facing a new Beis ha'Kisei. (It was not used yet.)

Question: Ravina never resolved whether or not Hazmanah (designation) for a Beis ha'Kisei takes effect (to forbid it like a Beis ha'Kisei)!

Answer: His was unsure whether one may pray inside it, but surely one may pray facing it.

(Rava): Even if there is excrement in a Persian latrine, it is considered sealed (so one may pray there).

Nedarim 7a - Question (Ravina): Do Yados work for (Hazmanah of) Beis ha'Kisei?

The case is, he said "this Bayis (enclosure) will be a Beis ha'Kisei, and this one."

Rishonim

R. Yonah (Berachos 17b DH v'Davka): An old Beis ha'Kisei is forbidden even if now there is no excrement in it, due to "v'Hayah Machanecha Kodesh." Whatever the Torah forbids, also four Amos facing it is forbidden. A new Beis ha'Kisei is permitted even inside, and all the more so facing it. Persian latrines, even if there is excrement in them, are considered sealed. Chachamim of France say that even though our privies are like the Persians', since there is always urine there, we do not consider them to be sealed, and they are forbidden. Rav Hai Gaon says that theirs were on an incline, so the urine descends immediately, therefore they are considered sealed, and they are permitted. Ours are not on an incline, so they are forbidden.

Rosh (Berachos 3:57): Rav Chisda permitted while facing a Beis ha'Kisei without excrement inside, and we established this to discuss a new Beis ha'Kisei.

Tosfos (Sukah 36b DH b'Shabbos): Rashi explains that we permit entering three rocks into a Beis ha'Kisei, within four Amos. The Beis ha'Kisei is in the field, without walls, so the only concern is Muktzeh. I say that 'entering' connotes that there are walls. Beis ha'Kisei connotes that it is a Bayis (i.e. has walls). Also Tamid 27a connotes that there are walls. It was enacted that women talk in the Beis ha'Kisei, to avoid seclusion (with men - Sanhedrin 19a). This connotes it was a covert place surrounded by walls, and people outside could not see in. It was a Reshus ha'Yachid; Chachamim permitted bringing rocks from a Karmelis, for the sake of dignity.

Poskim

Shulchan Aruch (OC 83:1): One may not read (Kri'as Shma) facing an old Beis ha'Kisei, even if the excrement was removed.

Mishnah Berurah (1): One may not read if it is within his sight in front of him, or within four Amos in back of him, or within four Amos of where the smell ends.

Kaf ha'Chayim (2): Even if the Beis ha'Kisei was washed and plastered, once it was Nidcheh (forbidden to pray in), it is never permitted.

Kaf ha'Chayim (4): If the excrement goes into a pit less than 10 Tefachim deep, it is not clear whether one may read near it.

Shulchan Aruch (ibid.): It seems that this is only if it has no walls. If it has walls, even if there is excrement inside, one may read without concern, if the smell does not reach him.

Beis Yosef (DH Mashma): We forbid Kri'as Shma facing a Beis ha'Kisei only if it has no walls, like those in the days of the Gemara. If it has walls, like ours, it is a Reshus unto itself. Even if there is excrement inside, one may read facing it, nearby. Since the wall separates, it is a separate Reshus. A proof is that Rava taught that if excrement is in front of him, he must distance himself as far as he can see, and we challenged him from Rav Chisda's Heter to pray facing a Beis ha'Kisei. If the Beis ha'Kisei has walls, this is not difficult! Rather, their Stam Beis ha'Kisei had no walls. If so, Rav Chisda permitted when excrement is in front of him, unlike Rava.

Rebuttal (Magen Avraham 1): We need not say so. Perhaps there are no walls, and there is no excrement inside! Rather, the questioner assumed that a Beis ha'Kisei is like excrement. The question from Rav Yosef proves this. If so, even if it has walls, they are like excrement.

Beis Yosef (ibid.): Perhaps even if the walls are not 10 Tefachim tall, if the ground of the Beis ha'Kisei cannot be seen, it is permitted. This is like one who covered excrement or urine with a Kli. He may read nearby. Even though we could say that a Beis ha'Kisei is more stringent, for even if there is no excrement there, one may not read facing it. However, since walls block view of the ground, it is reasonable that one may read.

Bach (1): If a Beis ha'Kisei had excrement in it, even if it was removed, it is as if the excrement is still there. Therefore, one must distance as far as he can see if it is in front of him, or four Amos from where the smell ends if it is in back of him. I say that even in the days of the Gemara, there were walls around the Beis ha'Kisei. Berachos 62a discusses R. Akiva entering a Beis ha'Kisei after R. Yehoshua. Entering applies only to a place with walls! However, they were less than 10 Tefachim, therefore a Beis ha'Kisei is considered like excrement.

Taz (1): The Beis Yosef and Bach overlooked Tosfos, who says that the Beis ha'Kisei was surrounded by walls. He calls it a Reshus ha'Yachid. Therefore, even with walls above 10 Tefachim it is forbidden. How can the Beis Yosef permit with walls less than 10? We forbid a Beis ha'Kisei even without excrement. Walls that block visibility of excrement are no better than a Beis ha'Kisei without excrement! Also, the Gemara then discusses Persian latrines. Surely they had walls, for the Tur learns from it to our privies! Persian latrines are permitted only because they are dug out, but not due to the walls. Rather, a Beis ha'Kisei is like excrement, even if it has a 10 Tefachim wall. Since the walls are made to receive excrement, it is like excrement, even if the wall is 10. It is like a bench with a hole (to sit on while eliminating) or a potty. The Beis Yosef (87) brought from the Rosh that since it is special for excrement, it is like a Beis ha'Kisei, even if no bad smell exudes. It seems that the walls are like a Beis ha'Kisei only if they were made only for the Beis ha'Kisei. However, if one used a wall of a house for a wall of a Beis ha'Kisei next to it, the wall is not like a Beis ha'Kisei. One may read even next to it. I discuss a Beis ha'Kisei in which the excrement rests on the ground (it does not fall in a pit), like in the days of the Gemara.

Magen Avraham (1): One should be stringent like the Bach. The Gemara connotes that walls do not help. They themselves are like a potty. We forbid walls of an old Beis ha'Kisei just like (inside) a new Beis ha'Kisei. Rashi (25a) and the Ba'al ha'Ma'or say 'there are walls between him and the Beis ha'Kisei. He stuck his hand past the wall.' They did not say that the Beis ha'Kisei has walls, for its walls do not help. The Rashba and Tosfos say that a Stam Beis ha'Kisei has walls. If Beis ha'Kisei is without walls, and it refers to where he sits, what was Ravina's question about designating a Bayis for a Beis ha'Kisei? Do not say that when it has walls, one may not read inside them even for a new Beis ha'Kisei. If so, surely Rav Chisda discusses when there are no walls, and Ravina discusses when there are walls and forbids within them, for outside is permitted even for an old Beis ha'Kisei. (However, the Gemara suggested that Ravina should have resolved his question from Rav Chisda's law!) Also, if walls forbid inside a new Beis ha'Kisei, what is the source to permit outside the walls for an old Beis ha'Kisei?! Therefore, even if the walls are 10 Tefachim tall, I forbid. Also Divrei Chamudos (Berachos 3:168) forbids. Surely one may not be lenient if they are less than 10 Tefachim. If a bad smell exudes, all forbid.

Mishnah Berurah (4): The walls reach the ground, or come within three Tefachim of the ground, so Lavud applies. (It is as if they touch the ground.)

Mishnah Berurah (5): All the Acharonim forbid if the walls are less than 10. Many are stringent even if they are 10. One should be stringent if a window of his house is open to a Beis ha'Kisei. In pressed circumstances, one may be lenient if no smell reaches him, for it is a Sefek-Sefeka (two doubts). Perhaps the Halachah follows the Beis Yosef and Bach, or perhaps the Halachah follows the Rosh, who permits when the excrement is in another Reshus. All permit if he closes his eyes.

Kaf ha'Chayim (4): If there is a wall around the Beis ha'Kisei, and nearby is a Beis ha'Keneses within Mechitzos, it is permitted, for there are two separations, as long as one cannot smell the excrement.

Bi'ur Halachah (DH v'Yir'eh): Some people clean the Beis ha'Kisei and make a Sukah there. This does not help, for it is an old Beis ha'Kisei, and after Sukos it will resume to be a Beis ha'Kisei. Panim Me'iros (1:87) says that one can uproot the name Beis ha'Kisei from a place. Even if you will say that this (cleaning it, and building a Sukah) uproots the name, one must check and clean the walls.

Bi'ur Halachah (DH Aval): The Pri Megadim was unsure whether four walls are needed, or if three suffice.

Bi'ur Halachah (DH Im): Most hold that walls of a Beis ha'Kisei do not separate (Reshus regarding) a bad smell, therefore one must distance four Amos from where the smell ends.