I use tap water as well but I let it sit in the open air for at least 24 hours.  The chlorine in the water will evaporate away and your plants will have an easier time absorbing the water and nutrients.  I keep at least 6 1 gallon jugs and a 3 gallon jug full at all times and they usually sit for a couple days before using them.  I have tried water straight from the tap and had all kinds of issues with my plants.