The city uses chloramine to treat the water, so I'm a bit hesitant to use it at all, though I do now have a faucet filter. Use one campden tablet per 20 gallons of water (less water is fine) to remove the chloramines.
I read somewhere (possibly Snyder's Brewmaster's Bible
?) that campden tablets were best avoided. Possibly this had to do with sensitivities to sulfites? Honestly, I'm not fond of my local water anyway, so I'll probably stick with purchased "drinking water" for brewing until I move to an area with better water or move to a house where I can install an RO unit.