There is a huge difference between RO and anybody's tap water. There are tons of things in tap water that you really don't want in your tank. Take a look around maybe there is a store that sells RO water. I know it may be tough in NYC, but here locally we have a store called Home Enviroment that sells RO for $.44 a gallon and even cheaper if you buy volume. I think they are a franchise, but I don't know if they are out your way.