I don't recommend using spring water. If you are purchasing water to top off your tank I recommend using distilled water.
Although spring water is clean enough to drink, doesn't mean that it is free of all contaminents. There may be no bacteria in it but may contain heavy metals, phosphates, and nitrites/nitrates. Which may be harmless for human consumption, but are not recommended for your saltwater tank.
Buy an RO/DI system as soon as you can, if you plan on staying in the hobby.
It will pay for it self in fuel cost alone. But until then buy RO/DI from the local fish store or use distilled water.