Class D Water License – Texas
Questions and Answers | Latest
Version | 2025/2026 | Correct & Verified
What is the maximum contaminant level goal (MCLG) for coliform bacteria?
✔✔Zero.
How often must water systems collect bacteriological samples?
✔✔At least once per month, depending on system size.
What is the minimum number of routine bacteriological samples required each month?
✔✔At least one.
What is the purpose of flushing water mains?
✔✔To remove sediment, stale water, and improve chlorine residuals.
What is the main function of a storage tank?
✔✔To maintain water pressure and provide reserve supply.
1
,What should be done immediately if a chlorine leak is suspected?
✔✔Evacuate the area and follow emergency response procedures.
What is the purpose of a water meter?
✔✔To measure the amount of water used by a customer.
What is the primary responsibility of a Class D water operator?
✔✔To provide safe, clean drinking water to the public.
What is the minimum required pressure for a public water system in Texas?
✔✔20 psi.
What is the recommended pressure range for a water distribution system?
✔✔35 to 80 psi.
What is the minimum free chlorine residual required in a Texas distribution system?
✔✔0.2 mg/L.
2
,What is the maximum chlorine residual allowed in drinking water?
✔✔4.0 mg/L.
What is the minimum contact time for chlorine disinfection before water enters the system?
✔✔At least 30 minutes at normal operating conditions.
What does TCEQ stand for?
✔✔Texas Commission on Environmental Quality.
What is the maximum contaminant level for nitrate in drinking water?
✔✔10 mg/L as nitrogen.
What is the maximum contaminant level for fluoride in drinking water?
✔✔4.0 mg/L.
What is the maximum contaminant level for lead in drinking water?
✔✔0.015 mg/L.
3
, What is the maximum contaminant level for copper in drinking water?
✔✔1.3 mg/L.
What is the purpose of chlorine in a water system?
✔✔To kill or inactivate harmful microorganisms.
What is a cross-connection in a water system?
✔✔A physical connection between drinking water and a potential source of contamination.
What is backflow?
✔✔The reverse flow of water or contaminants into the drinking water system.
What is the purpose of a backflow prevention device?
✔✔To stop contaminants from entering potable water lines.
What does coliform bacteria in a water sample indicate?
✔✔Possible contamination and presence of harmful pathogens.
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Questions and Answers | Latest
Version | 2025/2026 | Correct & Verified
What is the maximum contaminant level goal (MCLG) for coliform bacteria?
✔✔Zero.
How often must water systems collect bacteriological samples?
✔✔At least once per month, depending on system size.
What is the minimum number of routine bacteriological samples required each month?
✔✔At least one.
What is the purpose of flushing water mains?
✔✔To remove sediment, stale water, and improve chlorine residuals.
What is the main function of a storage tank?
✔✔To maintain water pressure and provide reserve supply.
1
,What should be done immediately if a chlorine leak is suspected?
✔✔Evacuate the area and follow emergency response procedures.
What is the purpose of a water meter?
✔✔To measure the amount of water used by a customer.
What is the primary responsibility of a Class D water operator?
✔✔To provide safe, clean drinking water to the public.
What is the minimum required pressure for a public water system in Texas?
✔✔20 psi.
What is the recommended pressure range for a water distribution system?
✔✔35 to 80 psi.
What is the minimum free chlorine residual required in a Texas distribution system?
✔✔0.2 mg/L.
2
,What is the maximum chlorine residual allowed in drinking water?
✔✔4.0 mg/L.
What is the minimum contact time for chlorine disinfection before water enters the system?
✔✔At least 30 minutes at normal operating conditions.
What does TCEQ stand for?
✔✔Texas Commission on Environmental Quality.
What is the maximum contaminant level for nitrate in drinking water?
✔✔10 mg/L as nitrogen.
What is the maximum contaminant level for fluoride in drinking water?
✔✔4.0 mg/L.
What is the maximum contaminant level for lead in drinking water?
✔✔0.015 mg/L.
3
, What is the maximum contaminant level for copper in drinking water?
✔✔1.3 mg/L.
What is the purpose of chlorine in a water system?
✔✔To kill or inactivate harmful microorganisms.
What is a cross-connection in a water system?
✔✔A physical connection between drinking water and a potential source of contamination.
What is backflow?
✔✔The reverse flow of water or contaminants into the drinking water system.
What is the purpose of a backflow prevention device?
✔✔To stop contaminants from entering potable water lines.
What does coliform bacteria in a water sample indicate?
✔✔Possible contamination and presence of harmful pathogens.
4
