Tap water?

I am using tap water for my 40g. I know I shouldn't use tap water, but my lfs is 1hour away (2hour round trip) so I can't go there every time I need to do a water change. :( Is the tap water ok. Is there anything I can do to treat it? Also, I have had a two-month cyano outbreak, and I have tried everything to get rid of it and I can't. I have used 4 different medications, Blacked out the tank, Done 20% water changes for a month. I am running a sump and skimmer. All of my levels are fine.