Non-potable water

I just walked by a sign by some hydrants feeding a garden that says, "Warning! Do not drink! Non-potable water."

I guess I'm stupid because I don't see how the water can be used to water the veggie garden which absorbs some nutrients (and whatever makes the water non-potable) from the watered soil BUT this same water cannot be potted.

I guess I need to Google it when I get home.

Sent on the Sprint® Now Network from my BlackBerry®