A properly installed and maintained system for treating and disposing of household wastewater will minimize the impact of that system on ground water and surface water. State and county codes specify how wastewater systems must be designed, installed and maintained. All new systems must be installed by a state certified installer and inspected by a state certified inspector prior to use. At a minimum, follow the Texas Natural Resource Conservation Commission codes for design and construction, but also consider whether the minimum requirements are sufficient at your site.