How does ADH work in water balance?

ADH increases the amount of water reabsorbed from the tubular filtrate back into the plasma decreasing urine production. This is achieved by increasing the permeability of the walls of the distal convoluted tubule (DTC) and the collecting duct (CD). This allows more water to be reabsorbed back into the blood from the of the distal convoluted tubule and the collecting duct.

High levels of ADH increases the permeability of the DCT and the CD, increasing the reabsorption of water back into blood capillaries, raising water concentration plasma levels and decreasing urine production.

Low levels of ADH decrease the permeability of the DCT and the CD, decreasing the reabsorption of water back into blood capillaries, lowering water concentration plasma levels and increasing urine production.