Kolel L'horaah Ma'asis Crown Heights - Shiur 7 on halachic topics - by Rabbi Shraga Dovid Homnick, Sgan Rosh Kolel, with a lengthy introduction on the question of stringencies and leniencies in mikvaos in general, and part one of a historical overview of the widespread early American practice of relying on city water for mikvahs

https://www.youtube.com/watch?v=PEP3plH95fk