According to this article, Aruch Hashulchan allowed municipality water to be used for a mikvah. Below is the direct quote from the article. Where can this Aruch Hashulchan be found?
In the late 19th century, Rabbi Yehiel Michel Epstein (1829-1908), author of Arukh Hashulhan, declared unequivocally that water supplied from a system of pipes that channel water from a river to houses throughout a city can be used for a mikveh, provided that either the tube that feeds into the mikveh is affixed to the ground, or that the final three handbredths of that tube where it pours into the cistern is made out of a material that is not succeptible to tumah, such as wood.
