Machshirin 2:1-2

Machshirin 2:1

Drippings from houses, wells, trenches and caves do not render food susceptible to ritual impurity, nor does human sweat. If one drank ritually unclean water and perspired, his sweat is ritually clean. If one walked through drawn water and perspired, his sweat is ritually unclean; if he dried himself first and perspired after, then his sweat is ritually clean.

Machshirin 2:2

Drippings from a ritually unclean bathhouse are ritually unclean; ki yutan applies to those of a ritually clean bathhouse. Let’s say that there’s a pool of water in a house and it causes the house to drip. If the pool is ritually unclean, then all the drippings in the house caused by the pool are unclean.