Final answer:
TCEQ requires that backflow prevention assemblies for health hazards be tested annually to protect the public water system from contamination.
Step-by-step explanation:
The Texas Commission on Environmental Quality (TCEQ) mandates that backflow prevention assemblies installed for health hazards must be tested annually. This is to ensure that they are functioning properly and to prevent any contamination of the public water system. Backflow prevention devices protect water supplies from contamination or pollution due to backflow, by preventing water from reversing flow and entering the clean water supply. It is crucial for facilities that pose a health hazard to have their backflow prevention assemblies working flawlessly, thus the stringent requirement for annual testing.