I read a book by Rabbi David Miller (1869 – 1939) ( he had semicha from Rabbi Isaac Elchanan of Kovno ) , The Secret of the Jew, which says you can fill an empty mikveh straight from a faucet (see pages 366 and 428). There is a copy of the book on Hebrew Books.
Are there opinions that argue on Rabbi Miller? Who are they, and what is the basis of their disagreement?
I ask because I've got the impression that all modern mikvah's are filled exclusively with rainwater, and that filling from zero with the faucet isn't done. I'm interested specifically in a mikvah used for nidah.