The Hero must go around Moresby and close the five leaking hydrants.
The Hero will be given waypoints on the mini-map, each leading to a busted fire hydrant, and a mob of the undead. There are five hydrants in total, and many of them have Infected or Thugs looming near them. After the fifth hydrant has been shut off, the quest will lead you full-circle back to the church. Completing the quest will reward the Hero with 4500XP and the Meat Bait schematic. This quest is part of the main storyline, and completion is required to move on to the next main quest.
You can basically use the car in the Pump Station to drive to each hydrant. With careful driving, this quest can be done easily.
You must close the hydrants in the order indicated by the quest marker. They are not available in any other order. What this means is you cannot grab the hydrant to shut it off if it's not the next one in order (it's still present, along with its undead guards).
None of the hydrants are spouting water until this quest is accepted.