How does water quality affect tomatoes?

Galen L asked:


We are getting ready to plant our first garden (Yippy!!) and of course we are looking forward to a bounty of tomatoes. However, we have a shallow well and the water is undrinkable due to high salt content (it might also be high in iron – I suppose need to get it tested?). I am concerned how this might affect our garden when we need to water it off our well water.