Stage 1 Disinfectants and Disinfection Byproducts Rules (DBPRs) apply to community water systems and non-transient non-community systems, including those serving fewer than 10,000 people, that add a disinfectant to the drinking water during any part of the treatment process. 

What to Do If There's an Exceedance

Chlorine or Chloramine Maximum Residual Disinfectant Level (MRDL)

If the quarterly running annual average (RAA) for chlorine/chloramine exceeds the MRDL of 4 mg/L, the system is in violation and must:

• Notify the regulatory agency contact
• Post a Tier 2 public notice for as long as the violation or situation persists, but in no case for less than seven days, even if the violation or situation is resolved (for community water systems or non-transient non-community water systems)
• Provide a certificate of public notice distribution to the regulatory agency as soon as practical, but no later than 30 days after the system learns of the violation

Chlorine Dioxide or Chlorite Daily at Entry Point to the Distribution System (EPDS)

If the daily chlorine dioxide sample taken at the EPDS exceeds the maximum residual disinfectant limit (MRDL) of 0.8 milligrams per liter (mg/L), the system must:

• Sample three follow-up chlorine dioxide samples in the distribution system the following day, in addition to the sample required at the EPDS (distribution system sampling locations are specified in your DBP Stage 1 Monitoring Plan)
• Notify the regulatory agency contact

If any of the three follow-up distribution samples of chlorine dioxide taken in the distribution system exceeds the MRDL of 0.8 mg/L, the system is in violation and must:

• Notify the regulatory agency contact
• Post a Tier 1 public notice for as long as the violation or situation persists, but in no case for less than seven days, even if the violation or situation is resolved
• Provide a certificate of public notice distribution to the regulatory agency no later than 24 hours after the system learns of the violation

Chlorite Daily EPDS

If the daily chlorite sample taken at the EPDS exceeds the maximum contaminant limit (MCL) of 1 mg/L, the system must:

• Sample three follow-up chlorite samples in the distribution system the following day, in addition to the sample required at the EPDS (distribution system sampling locations are specified in your DBP Stage 1 Monitoring Plan)
• Notify the regulatory agency contact​

​If the average of the three follow-up distribution samples of chlorite taken in the distribution system exceeds the MCL of 1 mg/L, the system is in violation and must:

• Notify the regulatory agency contact
• Post a Tier 2 public notice for as long as the violation or situation persists, but in no case for less than seven days, even if the violation or situation is resolved (for community water systems or non-transient non-community water systems)
• Provide a certificate of public notice distribution to the regulatory agency as soon as practical, but no later than 24 hours after the system learns of the violation

Chlorine Dioxide or Chlorite Distribution

If the average of the three chlorite samples taken in the distribution system exceeds the MCL of 1 mg/L, the system is in violation and must: 

• Notify the regulatory agency contact
• Post a Tier 2 public notice for as long as the violation or situation persists, but in no case for less than seven days, even if the violation or situation is resolved (for community water systems or non-transient water systems)
• Provide a certificate of public notice distribution to the regulatory agency as soon as practical, but no later than 30 days after the system learns of the violation

Bromate Distribution

If the running annual average of four quarters of monthly samples exceeds the MCL of 0.010 mg/L, the system is in violation and must:

• Notify the regulatory agency contact
• Post a Tier 2 public notice for as long as the violation or situation persists, but in no case for less than seven days, even if the violation or situation is resolved (for community water systems or non-transient water systems)
• Provide a certificate of public notice distribution to the regulatory agency as soon as practical, but no later than 30 days after the system learns of the violation