Class D Water Operator License Exam
TCEQ Questions and Answers | Latest
Version | 2025/2026 | Correct & Verified
What is the primary responsibility of a Class D water operator?
✔✔To provide safe and reliable drinking water to the public.
Who regulates public water systems in Texas?
✔✔The Texas Commission on Environmental Quality (TCEQ).
What is the maximum contaminant level for nitrate in drinking water?
✔✔10 mg/L as nitrogen.
What is the recommended minimum chlorine residual in a distribution system?
✔✔0.2 mg/L free chlorine.
What is the maximum allowable turbidity level for filtered water?
✔✔0.3 NTU in 95% of samples.
1
,What type of pipe material is commonly used for water mains in distribution systems?
✔✔PVC or ductile iron.
What is the minimum pressure that must be maintained in a water distribution system?
✔✔20 psi.
What does cross-connection control prevent?
✔✔Contamination of the drinking water system.
What is the main purpose of flushing fire hydrants?
✔✔To maintain water quality and remove sediments.
What is backflow in a water system?
✔✔The reversal of water flow into the distribution system.
What is the purpose of a storage tank in a water system?
✔✔To maintain pressure and provide supply during peak demand.
2
,What is the maximum contaminant level for arsenic in drinking water?
✔✔0.010 mg/L.
What chemical is most commonly used to disinfect drinking water?
✔✔Chlorine.
What is the main purpose of a pressure reducing valve?
✔✔To protect pipes by lowering water pressure in a system.
What is the main function of a well pump?
✔✔To lift groundwater to the distribution system.
What is the recommended pH range for drinking water?
✔✔6.5 to 8.5.
What is the purpose of a sanitary seal on a well?
✔✔To prevent surface contamination from entering the well.
3
, What is the purpose of a distribution system map?
✔✔To locate water lines, valves, and hydrants.
What is the maximum contaminant level for fluoride in drinking water?
✔✔4.0 mg/L.
What is the most common cause of low chlorine residual in a distribution system?
✔✔High water age or excessive demand.
What is the minimum free chlorine residual required at the entry point to a distribution system?
✔✔0.5 mg/L.
What does TCEQ require water operators to maintain for compliance?
✔✔Accurate records of water quality, operations, and maintenance.
What is the function of a SCADA system in water operations?
✔✔To monitor and control water system processes remotely.
4
TCEQ Questions and Answers | Latest
Version | 2025/2026 | Correct & Verified
What is the primary responsibility of a Class D water operator?
✔✔To provide safe and reliable drinking water to the public.
Who regulates public water systems in Texas?
✔✔The Texas Commission on Environmental Quality (TCEQ).
What is the maximum contaminant level for nitrate in drinking water?
✔✔10 mg/L as nitrogen.
What is the recommended minimum chlorine residual in a distribution system?
✔✔0.2 mg/L free chlorine.
What is the maximum allowable turbidity level for filtered water?
✔✔0.3 NTU in 95% of samples.
1
,What type of pipe material is commonly used for water mains in distribution systems?
✔✔PVC or ductile iron.
What is the minimum pressure that must be maintained in a water distribution system?
✔✔20 psi.
What does cross-connection control prevent?
✔✔Contamination of the drinking water system.
What is the main purpose of flushing fire hydrants?
✔✔To maintain water quality and remove sediments.
What is backflow in a water system?
✔✔The reversal of water flow into the distribution system.
What is the purpose of a storage tank in a water system?
✔✔To maintain pressure and provide supply during peak demand.
2
,What is the maximum contaminant level for arsenic in drinking water?
✔✔0.010 mg/L.
What chemical is most commonly used to disinfect drinking water?
✔✔Chlorine.
What is the main purpose of a pressure reducing valve?
✔✔To protect pipes by lowering water pressure in a system.
What is the main function of a well pump?
✔✔To lift groundwater to the distribution system.
What is the recommended pH range for drinking water?
✔✔6.5 to 8.5.
What is the purpose of a sanitary seal on a well?
✔✔To prevent surface contamination from entering the well.
3
, What is the purpose of a distribution system map?
✔✔To locate water lines, valves, and hydrants.
What is the maximum contaminant level for fluoride in drinking water?
✔✔4.0 mg/L.
What is the most common cause of low chlorine residual in a distribution system?
✔✔High water age or excessive demand.
What is the minimum free chlorine residual required at the entry point to a distribution system?
✔✔0.5 mg/L.
What does TCEQ require water operators to maintain for compliance?
✔✔Accurate records of water quality, operations, and maintenance.
What is the function of a SCADA system in water operations?
✔✔To monitor and control water system processes remotely.
4
