Disruption of Service

A “disruption of service” means an event during which the minimum pressure at any point in the distribution system falls below 20 psig at ground level. They can be caused in a variety of ways such as a waterline break, power outage, equipment failure, etc. Regardless of the cause, disruptions of service pose a public health risk. The disruption of service rule (OAC Rule 3745-83-02) was developed to mitigate this risk and includes response requirements for all public water systems. These requirements are summarized below and include the 2024 rule revisions (Effective December 12, 2024). Please contact your Ohio EPA District Office with any questions.

The rule replaces Ohio EPA’s “Policy for Evaluating and Responding to Water Distribution Systems and Subsystems that have Depressurized” OPR-06-001.

The rule requirements vary depending on the type of system and are grouped as follows:

1. “Small Systems” = All transient noncommunity (TNC) public water systems (PWSs) and nontransient noncommunity (NTNC) PWSs serving a population under 1,000
2. “Large Systems” = NTNCs serving a population of 1,000 or more, and all community PWSs

Affected Area vs. Impacted Service Area

The rule requirements can vary for those in the affected area versus those in the impacted service area. Therefore, it’s important to understand the difference between these two areas:

• “Affected area” = The portion of the distribution system where the pressure has dropped below 20 psig at ground level.
• “Impacted service area” = Any service line that has been moved, replaced, or reconnected to the main during a main replacement. Includes any buildings, residences, or lines served by the impacted service line.

The affected area may be larger than or equivalent to the impacted service area. The affected area could include the entire distribution system if the whole system loses pressure (e.g., power outage, tower drained, etc.), or it could include a small portion (e.g., able to valve off the area before losing pressure). “Large Systems” are required to monitor the pressure upstream and downstream of the area during a disruption of service to determine the extent of the affected area.

The impacted service area only exists if there are service lines on the section of water main being replaced. If the PWS does not need to conduct a main replacement or if there are no service lines on the portion of main being replaced, then there is no impacted service area.

Small Systems

"Small Systems" have five main steps to follow if they have a disruption of service. These steps are summarized in the "Small Systems Flowchart".

1. Implement an acceptable temporary remedy within 24 hours.

   "Small Systems" are required to implement a temporary remedy within 24 hours of the beginning of the disruption of service. Options include:

   • Temporarily close
   • Provide bottled water
   • Another acceptable remedy (Contact your drinking water inspector for prior approval)

   If the PWS remains open, it is recommended to issue a precautionary water use advisory. The temporary remedy must be in place until the PWS receives E. coli-negative (EC-) sample results. 

2. Restore pressure to at least 20 psig throughout the distribution system.

   Take action to ensure the pressure is restored to at least 20 psig throughout the distribution system. This could include calling in a contractor, calling your utility company, etc. 

   If a well driller is needed for work on the well, they must be registered with the Ohio Department Health (ODH). Consult the list of ODH registered well drillers. Ensure the contractor has a check mark under the "well" column of that website. 

3. Complete the disinfection procedure for well work, if applicable.

   If work is done on the well that could result in contamination entering the well (well alteration, repair, replace pitless adapter, replace portion of casing, etc.), the PWS must complete the well disinfection procedure in OAC Rule 3745-9-08 (disinfecting well for at least 8 hours, flushing for at least 15 minutes, etc.). This procedure is summarized in the "Disinfection of a Public Water System Well" document. 

   Part of these requirements is to not place the well back into service until at least 2 consecutive raw total coliform samples collected at least 30 minutes apart are TC-. These are raw samples (before any treatment) and are required in addition to the distribution samples in Step 5 below. The PWS can choose to collect these 2 raw samples on the same day as collecting the distribution samples or wait to collect the distribution samples until after they receive safe raw sample results. Reference the "Disinfection of a Public Water System Well" document for next steps based on the sample results. 

4. Complete lead requirements, if applicable, at an NTNC. 

   If a NTNC has a disruption of service that meets the definition of a Type 2 or Major Disruption Event that coincides with a lead service line (LSL) replacement or a main replacement in an area with LSLs, the PWS may need to complete lead requirements in addition to the disruption of service requirements. The PWS should reference the lead guidance, "Guidelines for Water Line Repairs and Replacements in Areas with Lead Service Lines."

   The water use advisory templates listed in the guidance incorporate both the lead language and the disruption of service language. 

5. Collect total coliform samples in the affected area.

   After any repairs are complete and pressure has been restored to 20 psig throughout the distribution system, "Small Systems" are required to collect total coliform samples from representative locations in the affected area of the distribution system. The total coliform samples should be marked as follows:

   • Sample Type = Special
   • Facility Code/Facility ID = DS1
   • Sample Monitoring Point (SMP) = DS000

   The minimum number of special purpose total coliform samples is listed in Table 1:

   Table 1. Total Coliform Distribution Sampling from Affected Area.

   Service Connections Affected	Minimum Number of Total Coliform Samples Required
   0 – 15	1
   16 – 1,000	2
   1,001 – 2,000	4
   2,001 – 3,000	6
   3,001 – 4,000	8
   4,001 – 5,000	10
   5,001 – 6,000	12
   6,001 – 7,000	14
   7,001 – 8,000	16
   8,001 – 9,000	18
   9,001 – 10,000*	20

   *After 10,000 service connections, two additional samples shall be added for every 1,000 service connections up to a maximum of 100 samples. Public water systems that have multiple treatment plants may use a proportional sampling method if established in the contingency plan or in the initial distribution system evaluation.

   The PWS would then complete the steps in Table 2 based on the sample results.

   Table 2. "Small System" Response Requirements from Total Coliform Sample Results.

   Results of Sampling	Response Requirements
   All samples are TC- (safe)	Can stop implementing the temporary remedy (See Step 1). Can lift the precautionary water use advisory (if one was issued).
   Any sample is TC+, and all are EC-	Can stop implementing the temporary remedy (See Step 1). Can lift the precautionary water use advisory (if one was issued), though can choose to keep it posted as a precaution.  Required to contact Ohio EPA and continue to monitor with an additional set of total coliform samples (See Table 1 above) until one complete set of samples is TC-. It is recommended to flush the distribution system prior to collecting a new set of samples.
   Any sample is EC+	Required to issue a water use advisory (Noncommunity Template) Consult with Ohio EPA. Collect two additional sets of samples, at least 24 hours apart. See Table 1 above for minimum number of samples required in each set; however, if 0 to 15 service connections are affected, collect a minimum of two samples per set.  Can lift the water use advisory once all samples in both sets are TC- and consulted with Ohio EPA. It is recommended to flush the distribution system prior to collecting a new set of samples.

Large Systems

Disruptions of service at “Large Systems” are broken down into three types:

1. Type 1 = A disruption of service where positive pressure is continuously maintained in the affected area, and there are no signs of contamination intrusion.

   • A Type 1 Event is the lowest risk to contamination intrusion. It means the pressure in the distribution system has fallen below 20 psig, but is above 0 psig, in the affected area and positive flow is maintained. This means that the water is flowing, even if it is flowing slowly. If the water stops flowing, it would be either a Type 2 (if positive pressure is maintained until the PWS can isolate the area) or a Major Disruption Event. 
   • There must also be no signs of contamination intrusion. For example, if muddy water enters the pipe during the repair, that would be considered contamination intrusion would be elevated to a Major Disruption Event. 

2. Type 2 = A disruption of service where positive pressure is maintained in the affected area until the affected area has been isolated from the rest of the distribution system and there are no signs of contamination intrusion.

   • The difference between a Type 1 and Type 2 Event is that the Type 2 Event starts off with positive pressure which is maintained until the affected area can be isolated. This generally means that the PWS is able to valve off the area before it loses pressure completely.
   • There must also be no signs of contamination intrusion. For example, if muddy water enters the pipe during the repair, that would be considered contamination intrusion would be elevated to a Major Disruption Event.

3. Major Disruption Event = Any disruption of service that is not a Type 1 or Type 2 Event.

Review the “Disruption of Service Type Flowchart” for assistance with determining which event type has occurred. 

Response Requirements

Type 1 Event Response

“Large Systems” are required to complete the following response actions for a Type 1 Event:

1. Excavate the pit to below the area to be repaired.
2. Maintain the water level in the pit below the area to be repaired.
3. Disinfect the line in accordance with AWWA Standard C651-14 Section 4.11.3.1.
4. Complete the repair under positive pressure.
5. After completing the repair, check the chlorine residual and ensure it is at least 0.2 mg/L free or 1.0 mg/L combined. 
6. Document the event afterwards using the online reporting tool (Note: The PWS can use their own internal system to document the event as long as it records the same information as the online reporting tool). 

Type 2 Event Response

“Large Systems” are required to complete the following response actions for a Type 2 Event:

1. Perform a controlled shutdown of the affected area.

2. In the case of waterline or appurtenance (valve, hydrant, etc.) repair or replacement:

   1. Excavate the pit to below the area to be repaired, 
   2. Maintain the water level in the pit below the area to be repaired, 
   3. Disinfect, repair, and flush the line in accordance with AWWA Standard C651-14 Section 4.11.3.2.
3. For emergency water main replacements areas known or likely to contain lead service lines (LSLs), or if the Type 2 Event is associated with an individual LSL replacement, consult the lead guidance (“Guidelines for Water Line Repairs and Replacements in Areas with Lead Service Lines”). If the lead guidance says to post a water use advisory, PWSs should use the templates in the lead guidance which include both the lead language and the disruption of service language. 

4. Notify critical users in the affected area asap, but within 24 hours. Critical users are consumers who have a critical need for water (e.g., hospitals, dialysis centers, homebound individuals). If critical users are in the affected area, they must be notified of Type 2 and Major Disruption Events as soon as possible, but within 24 hours. If possible, critical users should be informed before the disruption begins so they can plan accordingly (e.g., before valves are closed). 

   Nontransient noncommunity PWSs who serve at least 1,000 people may not have a contingency plan, and therefore, may not have critical users identified as part of that plan. However, these systems are required to notify consumers who have a critical need of water as soon as possible, but within 24 hours of a Type 2 or Major Disruption Event. Thus, they should prepare a list of any such users.

5. Check the chlorine residual after the repair and ensure it is at least 0.2 mg/L free or 1.0 mg/L combined.
6. Document the event afterwards using the online reporting tool (Note: The PWS can use their own internal system to document the event as long as it records the same information as the online reporting tool). 

Major Disruption Event Response

Ohio EPA Notification Criteria

Major Disruption Events must be called in to Ohio EPA as soon as possible, but within 24 hours, if they meet all three of the following criteria:

1. Repairs will not be complete within 24 hours of the beginning of the disruption of service event.

   This means the PWS knows the repairs will not be done within 24 hours (e.g., need to order a part that will not be delivered within 24 hours), or they determine over the course of the event that they will not finish the work in time (e.g., repairs are in progress, but will not be complete before the 24-hour mark). 

2. The PWS anticipates the affected area will be without water provided through the distribution system for more than 24 hours.

   There is a difference between being under a water use advisory (where the consumers have access to water and need to boil it) and not having water (where there is no water coming out of the faucet when consumers turn it on). If the PWS anticipates that there will be no pressure in the lines for more than 24 hours, then that would meet criteria #2.

   Providing bottled water or a fill station for consumers to fill water jugs does not qualify as “water provided through the distribution system.” Therefore, the PWS would still meet criteria #2 if they are providing water in ways other than through the distribution system. 

3. And, the affected area includes more than 250 service connections, or more than 25% of the population, whichever is least.

If all three of these criteria are met, the PWS must call Ohio EPA and speak with a person. They can speak with either the emergency hotline representative (1.800.282.9378) or someone else with Ohio EPA to satisfy this requirement. They cannot use email for this notification. Please reference the “Major Disruption Event Notification Flowchart” for assistance with determining if you are required to call in a Major Disruption Event.

“Large Systems” are required to complete the following actions for a Major Disruption Event:

1. Activate the notification procedures in their contingency plan.
2. Issue a precautionary water use advisory (Noncommunity Template; Community Template) to all potentially affected consumers asap, but within 24 hours. The notice must be issued to all service connections in the affected area. Therefore, this notification covers the requirement to notify critical users. However, efforts should still be made to notify critical users before the disruption, if possible.
3. Document any potential contamination.
4. If the disruption of service coincides with a main replacement in an area with LSLs, or with an individual LSL replacement, the PWS must consult the lead guidance and complete all applicable requirements (“Guidelines for Water Line Repairs and Replacements in Areas with Lead Service Lines”). If the lead guidance says to post a water use advisory, PWSs should use the template in the lead guidance which includes both the lead language and the disruption of service language. 
5. In the case of water main repairs or replacements, disinfect, repair, and flush in accordance with AWWA Standard C651-14 Section 4.11.3.3.
6. Community water systems: If a community PWS is not able to provide water through its distribution system within 24 hours from the beginning of a Type 2 or Major Disruption Event, it is required to provide water from an alternate source. PWSs should reference their contingency plan for a list of alternate sources and their plan for how to distribute the water. If the alternate source includes hauling in water, the PWS must use a water hauler approved by the Ohio Department Health (ODH) or their local health department. A list of approved haulers can be found on the ODH website or by contacting the local health department.

7. If work is done on the well that could result in contamination entering the well (well alteration, repair, replace pitless adapter, replace portion of casing, etc.), the PWS must complete the well disinfection procedure in OAC Rule 3745-9-08 (disinfecting well for at least 8 hours, flushing for at least 15 minutes, etc.). This procedure is summarized in the “Disinfection of a Public Water System Well” document. 

   Part of these requirements is to not place the well back into service until at least two consecutive raw total coliform samples collected at least 30 minutes apart are TC-. These are raw samples (before any treatment) and are required in addition to the distribution samples in Step 5 below. The PWS can choose to collect these two raw samples on the same day as collecting the distribution samples or wait to collect the distribution samples until after they receive safe raw sample results. Reference the “Disinfection of a Public Water System Well” document for next steps based on the sample results. 

8. Check the chlorine residual after the repair and ensure it meets the minimum and maximum disinfectant residual requirements (Minimum of 0.2 mg/L free or 1.0 mg/L combined; Maximum of 4.0 mg/L total chlorine or 0.8 mg/L chlorine dioxide). 

9. Collect special purpose total coliform samples at locations representative of the affected area in accordance with Table 1 after repairs are made, pressure has been restored to 20 psig or above and the chlorine residual is within acceptable limits. Complete any required actions in Table 3 based on the sample results. 

   The total coliform samples should be marked as follows:

   • Sample Type = Special
   • Facility Code/Facility ID = DS1
   • Sample Monitoring Point (SMP) = DS000

   Table 1. Total Coliform Special Purpose Sampling Requirements for Disruptions of Service.

   Service Connections Affected	Minimum Number of Total Coliform Samples Required
   0 – 15	1
   16 – 1,000	2
   1,001 – 2,000	4
   2,001 – 3,000	6
   3,001 – 4,000	8
   4,001 – 5,000	10
   5,001 – 6,000	12
   6,001 – 7,000	14
   7,001 – 8,000	16
   8,001 – 9,000	18
   9,001 – 10,000*	20

   *After 10,000 service connections, two additional samples shall be added for every 1,000 service connections up to a maximum of 100 samples. Public water systems that have multiple treatment plants may use a proportional sampling method if established in the contingency plan or in the initial distribution system evaluation.

   Table 3. “Large System” Response Requirements from Total Coliform Sample Results.

   Results of Sampling	Response Requirements
   All samples are TC-	Can lift the precautionary water use advisory (if one was issued)
   Any samples are total coliform positive (TC+) and all are EC-	Can lift the precautionary water use advisory (if one was issued), though can choose to keep it posted as a precaution.  Contact Ohio EPA and continue to monitor with an additional set of total coliform samples (See Table 1 above) until one complete set of samples is TC-. It is recommended to flush the distribution system prior to collecting a new set of samples.
   At least one sample is EC+	Required to issue a water use advisory (Noncommunity Template; Community Template).  Consult with Ohio EPA. Collect two additional sets of samples, at least 24 hours apart. See Table 1 above for minimum number of samples required in each set; however, if 0 to 15 service connections are affected, collect a minimum of two samples per set.  Can lift the water use advisory once all samples in both sets are TC- and the PWS consulted with Ohio EPA. It is recommended to flush the distribution system prior to collecting a new set of samples.

    

10. Document the event using the Ohio EPA online reporting tool. PWSs are required to report Major Disruption Events using the online reporting tool. They must submit the online report within 48 hours or the next business day, whichever is later, of the disruption of service being corrected (i.e., completed response actions and received safe total coliform sample results).

Additional Information for Large Systems

Disruption Type Elevation

If the PWS does not complete the response requirements for the applicable disruption of service type, the event is elevated to the next higher disruption type (e.g., Type 1 Event becomes a Type 2 Event, Type 2 Event becomes a Major Disruption Event). When an event is elevated, PWSs are required to follow the requirements of the elevated disruption type. For example, if pressure is not monitored, a Type 1 or Type 2 Event would be elevated to a Major Disruption Event. In that case, the response requirements for a Major Disruption Event must be completed. 

Monitoring Pressure

“Large Systems” are required to monitor pressure. For a disruption of service to be considered a Type 1 or Type 2 Event, the PWS must monitor pressure upstream and downstream of the area so they can determine the extent of the affected area and determine if a disruption of service has occurred. If the PWS fails to adequately monitor pressure, the event is elevated to a Major Disruption Event. 

There are multiple ways for a PWS to monitor pressure. Some acceptable examples include:

1. In-line pressure monitors with either a pressure gauge that can be manually read or with a sensor that connects to a SCADA system. 
2. Hydrant pressure recorders. These devices are typically battery powered. Some can wirelessly transmit data to provide alerts and alarms in response to pressure readings, while others must be connected to a portable device to view the data. 
3. Storage tank or water tower level. In some instances, the storage tank or water tower level can be used to monitor pressure. However, this method may not always be appropriate. Contact Ohio EPA to determine if this method is acceptable for the event.
4. Hydraulic model. PWSs who maintain a functioning and accurate hydraulic model can use that to identify the affected area. The PWS must have personnel knowledgeable in running the model available to run it during the disruption event. 

If the PWS wants to use an alternate method to those listed above, please contact your Ohio EPA drinking water inspector to determine if the alternative method is acceptable. 

Extent of Distribution System

For “Large Systems,” it is helpful to clarify the extent of the distribution system that falls under the disruption of service rule. There are two sides to a service line: the PWS-owned side (closest to the main) and the consumer-owned side (furthest from the main), which are generally separated by the curb stop (See Figure 1 below). 

Figure 1. Below ground service line serving a single building.

For disruptions of service, the distribution system includes the service line up to the curb stop. This is because PWSs can shut off service at the curb stop for a variety of reasons unrelated to a disruption of service. Before the curb stop should always be pressurized, however. Therefore, if the pressure falls below 20 psig before the curb stop, it is considered a disruption of service and the PWS would need to complete the applicable response requirements.