4. [The waters] from one vessel, from two, or from three combine, but from four they do not combine. [Similarly, regarding] a baal keri who was sick and nine kabin of water fell over him, or a person who was tahor and three lugin of drawn water fell over his head and the greater part of his body — [the waters] from one vessel, from two, or from three combine, [but] from four they do not combine. When are these words said? When the second [vessel] started [emptying] before the first one ceased. And when are these words said? When he had no intention to increase [the mikveh]. But if he intended to increase [it, additions of] even one kortov [at a time] all year long combine to three lugin.

1. [If] one placed vessels under a pipe — whether large vessels or small vessels, even dungware [or] stoneware [or] mudware — they disqualify a mikveh. Whether one placed [them] or one forgot [them], according to the words of Beis Shammai. Beis Hillel declare it tahor when he forgot [them]. R’ Meir said: They were counted and Beis Shammai outnumbered Beis Hillel. [However,] they agree that if he forgot [them] in a courtyard, it is tahor. R’ Yose said: The dispute still stands in its place.

2. [If] one placed a board under a pipe — if it has a rim, it disqualifies a mikveh; if not, it does not disqualify a mikveh. [If, however,] he stood it upright to rinse it off, [then] in either case it does not disqualify a mikveh.

3. [If] one hollowed out [a cavity] in a pipe to receive gravel — in a case that it is of wood, [it disqualifies a mikveh] whatever the size [of the cavity]; but in a case that it is earthenware, [it disqualifies a mikveh when the size of the cavity is] one reviis. R’ Yose says: Also in a case that it is earthenware, [it disqualifies a mikveh] whatever the size [of the cavity], [and] they spoke of a reviis only concerning broken vessels of earthenware. [If] the gravel in it was loose, it disqualifies a mikveh. [If] earth fell in it and was pressed down, [the mikveh] is [still] fit. A pipe which is narrow at both ends and wide in the middle does not disqualify [a mikveh], because it was not made to receive.