Texas does not require any sort of license or certification for those providing septic inspections. However, there IS a certification that is obtainable through NAWT (National Association of Wastewater Technicians/NAWT.org), which is highly recommended. There is a right way, and a lot of wrong ways, to perform septic inspections. This hole in the regulations leaves buyers and realtors in the dark. Often the person scheduling the inspection does not know the difference, and unfortunately, some companies take advantage of that.
If you receive a septic inspection report that is vague, or anytime a system fails inspection, it is recommended to obtain written information from the inspector on how the system was tested and why the inspector came to their conclusion. (Examples: What was the liquid level upon arrival, how much water was run through the system to test it, did the liquid level rise in the tank, was it pumped down to check for backflow from the absorption area, are baffles in place, etc.).
Although a NAWT certification is not required, it is recommended. It’s also recommended the inspector has a TCEQ installer license. However, many inspectors list license numbers that are not relevant to the service being performed, such as waste hauler permits that are required to haul waste in the vacuum trucks.
Do your research. Find out credentials and experience from your potential septic inspector before the inspection, otherwise, you could be left negotiating your home purchase based on false information due to inaccurate inspection procedures.