Machshirin 4:8-9

Machshirin 4:8

Let’s say that a clay pot of water was put into a mikvah. If a person who was a primary source of impurity (av hatuma) reached his hand into it, it is rendered ritually unclean. (A mikvah doesn’t purify earthenware.) If a person in the first degree of impurity (rishon) does so, the pot remains clean. If the pot contained any liquid other than water, they are rendered unclean because water doesn’t purify other liquids.

Machshirin 4:9

If a person filled water through a channel, for three days it renders produce susceptible to impurity (the channel takes three days to dry). Rabbi Akiva says that if one dried the channel, it is ritually clean right away; if he didn’t dry it, it can render unclean even after 30 days.