Protocol for the Collection, Transfer and ANSI/AARST MW-RN 2020 Measurement of Radon in Water 22 8. 5 All reports—Required guidance based upon concentrations measured The test report shall include equivalent statements for each of the guidance messages shown in the Tables 8. 5 .1 and 8. 5 .2 . If action level guidance or requirements established by the local health department are lower than 4,000 pCi/L (150 Bq/L) in water, the local action level shall be substituted or provided along with the name of the local state health department or authority that published such guidance or requirement. Table 8. 5 .1 For Concentrations of Radon in Water That Exceed 4,000 pCi/L (150 Bq/L) (or a lower action level recommended by local jurisdiction or state health department). EQUIVALENT STATEMENTS FOR THESE ADVISORIES SHALL BE INCLUDED IN THE REPORT • Take remedial action to reduce radon concentrations in potable water. Test results from two samples indicate concentrations that exceed an action level of 4,000 picocuries per Liter (pCi/L) in water. - If only a single sample is available, decisions to mitigate at any time are not prohibited. However, a second test aids confidence that decisions are not being made based on a faulty test result. - If one test result is above the action level with the other test result below the action level and the higher test result is twice or more than the lower test result, obtaining confirmation on whether mitigation is warranted requires additional testing. • Post-mitigation testing: The mitigation system is not complete until system effectiveness has been verified by testing. • It is critical to properly maintain the water mitigation system to protect occupants from hazards that can include radon, biological contaminants and other radiological concerns. The radon-in- water concentration should be tested no less than yearly and periodic testing twice a year is recommended to confirm that the system remains effective.