It turns out that fixing an old leaky spigot, even over a slab, is really easy. I let my 40 year old house's spigots leak for years before dealing with it, and it really just takes a few minutes of actual work so long as you're comfortable using big wrenches.
Check out this video that explains how to change the washer inside the spigot that shuts the water off.
https://www.youtube.com/watch?v=-OagTnL6yf0
