Water systems must not find more than what percent of the samples they collect for coliform testing each month to be coliform positive?

The correct answer is based on regulations established by the Environmental Protection Agency (EPA) and the guidelines for total coliform monitoring in drinking water systems. Water systems are required to adhere to a standard that stipulates no more than 5 percent of the samples collected for coliform testing each month can test positive for total coliform bacteria.

This standard helps ensure the safety and quality of drinking water. Total coliforms are used as an indicator of potential contaminations that may indicate the presence of harmful pathogens. A 5 percent threshold allows for the detection of issues without being overly stringent, which helps water systems maintain manageable operational practices while still protecting public health.

The other percentages mentioned are either too low or do not align with the accepted regulatory standards. A threshold of 1 percent or 3 percent would be overly restrictive, likely leading to more frequent and unnecessary alarms for water systems, while 10 percent would be too lenient, potentially endangering public health by allowing a higher level of contamination. Adhering to the 5 percent threshold provides a balance between operational feasibility and protection against potential health risks.