Yea I've been using tap water to top off and do water changes with whenever I don't have the time to get RO, i usually do one water change with RO, and the next with tap, and top off with tap water. I use seachem prime as a dechlorinator. I do this in my 29 gal mixed reef, have a lot of SPS that are encrusting and doing great.
I have 36-37 here in Bay Ridge but I would never think about using tap water in my tank. NYC water is one of the best in the country however it's very high sediments. Some people in other parts of the country like Arizona reports TDS in range of 500-600 or even higher.