Spray field layout — required coverage area, keeping spray within property, landscaping and planting restrictions over the field.

The spray field must be at least Q ÷ Ri square feet, on terrain sloping ≤15% (steeper only if landscaped and terraced to stop runoff), covered with grasses, evergreen shrubs, bushes, trees or landscaped beds of mixed vegetation, with nothing within 10 feet of a sprinkler that would interfere with uniform application; overlapping circular patterns may be used but overlapped area counts only once (TCEQ RG-472, §285.33(d)(2)). Spray is prohibited on land used for growing food, gardens, orchards, crops for human consumption, and unseeded bare ground — bare areas must be seeded or sodded and growing before start-up, and every application must include a landscape plan detailing the vegetation to be maintained (TCEQ RG-472; TCEQ, Choosing a Septic System). Containment is enforced through the Table X edge-of-spray setbacks (20 ft to property lines, 10 ft with a commercial timer spraying midnight–5:00 a.m.), low-angle nozzles with a trajectory of 15 degrees or less, maximum 40 psi sprinkler inlet pressure, rates adjusted so there is no runoff, purple-colored distribution components, buried piping with no hose bibs, and storage of one day's flow (timer systems) or a dosing volume of half the daily flow (non-timer) (TCEQ RG-472). Hays County adds a 15-ft sprinkler setback from trees 24 inches or greater in diameter, a maximum sprinkler operating height of 24 inches, and prohibits spray for commercial/institutional flows over 300 gpd (Hays County OSSF Regulations).

Reviewed August 2026. Links go to the sources this answer was checked against.