In Texas, no permit is required to use a greywater system when the flow is less than 400 gallons per day.

More information

Texas Health & Safety Code - Section 341.039. Graywater Standards



(a) The commission by rule shall adopt and implement minimum standards for the use and reuse of graywater for:
  (1)  irrigation and other agricultural purposes;                             
  (2)  domestic use, to the extent consistent with Subsection (c);           
  (3)  commercial purposes;  and                                               
  (4)  industrial purposes.                                                    
 (b)  The standards adopted by the commission under
Subsection (a) must assure that the use of graywater is not a nuisance and does not damage the quality of surface water and groundwater in this state.
 (c)  The commission may not require a permit for the domestic use of less than 400 gallons of graywater each day if the graywater:
  (1)  originates from a private residence;                                    
  (2)  is used by the occupants of that residence for gardening, composting, or landscaping at the residence;
  (3)  is collected using a system that overflows into a sewage collection or on-site wastewater treatment and disposal system;
  (4)  is stored in tanks that:                                                
   (A)  are clearly labeled as nonpotable water;                               
   (B)  restrict access, especially to children;  and                          
   (C)  eliminate habitat for mosquitoes and other vectors;                  
  (5)  uses piping clearly identified as a nonpotable water conduit, including identification through the use of purple pipe, purple tape, or similar markings;
  (6)  is generated without the formation of ponds or pools of graywater;    
  (7)  does not create runoff across the property lines or onto any paved surface;  and
  (8)  is distributed by a surface or subsurface system that does not spray into the air.
 (d)  Each builder is encouraged to:                                           
  (1)  install plumbing in new housing in a manner that provides the capacity to collect graywater from all allowable sources;  and
  (2)  design and install a subsurface graywater system around the foundation of new housing in a way that minimizes foundation movement or cracking.
 (e)  In this section, "graywater" means wastewater from clothes-washing machines, showers, bathtubs, hand-washing lavatories, and sinks that are not used for disposal of hazardous or toxic ingredients.  The term does not include wastewater:
  (1)  that has come in contact with toilet waste;                             
  (2)  from the washing of material, including diapers, soiled with human excreta;  or
  (3)  from sinks used for food preparation or disposal.

For the expert

Read the full version of the greywater regulation in Texas here.