Adoption of the 2013 plumbing code addresses Alternate Water Sources for Nonpotable Applications. A gray water system is designed to collect gray water and transport it out of the structure for distribution in an Irrigation or Disposal Field. A gray water system may include tanks, valves, filters, pumps, or other purtenances along with piping and receiving landscape. Simple laundry to landscape systems do not require a permit, but anything more complex will require Building and Environmental Health review and approval.