A water purification system is provided that includes a pre-filtration system for pre-filtering water, a first pump, a nano-filtration membrane configured to separate pre-filtered water into nano-filtered water and effluent, a holding tank, and a second pump. The first pump is operable for pumping pre-filtered water through the nano-filtration membrane, and the second pump is operable for pumping nano-filtered water from the holding tank into the plumbing of a building.