Mikvaos 6:6-7

Mikvaos 6:6

If there was a broken earthenware vessel in the mikvah and utensils were immersed in it, they are purified of their ritual uncleanliness but are rendered impure again because of the earthenware vessel. If water flowed over it in any volume, then the utensils are ritually clean. If a spring flowed from an oven and someone immersed in it, he is ritually clean but his hands are rendered unclean (by the airspace of the oven). If the water was over the oven by the height of his hands, then his hands also are purified.

Mikvaos 6:7

Mikvahs are joined by a hole the size of a waterskin’s spout in thickness and in empty space so that two fingers can be turned around in it. If there’s a doubt as to whether it’s as big as a waterskin’s spout, it’s invalid because this is a matter of Biblical law. The same is true of an olive-sized piece of a corpse, an olive-sized piece of carrion and a lentil-sized piece of vermin (i.e., cases of doubt are ruled stringently because these are matters of Biblical law). Anything that settles in the hole the size of a waterskin’s spout reduces its size (so that the mikvahs are no longer joined). Rabban Shimon ben Gamliel says that if it’s something that originates in the water, the mikvahs remain valid.