Water is directed to the tanks with either a Dry or Wet system. In a Dry system, the water from your roof is directed by gutters into the top of the tank. Typically, this means that the tanks are located next to the home and near the downspout. In a Wet system, the water from your roof is directed by gutters to the downspout. The downspout then runs underground to the tank. The tanks in a Wet system can be located farther away from the house.