AWWA C Disinfecting Water Mains. Current; Document Language: English; Published By: American Water Works Association (AWWA). This standard presents essential procedures for the disinfection of new and repaired potable water mains. All new water mains shall be disinfected before they. FIELD CHLORINATION. • AWWA/ANSI C – Disinfecting Water Mains. • First standard approved Sept. 30, • Latest revision June 1.

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Appendix B Tools to help determine the category of watermain break – pictures Examples of watermain breaks that are typical of Category 1 are included below for illustrative purposes only: Flow may be reduced by throttling valves while maintaining sufficient flow from the break to minimize the potential for Contamination. Category 1 watermain breaks are not defined as an observation of improper disinfection in accordance with Section of Schedule 16 of O. Tags Environment and energyDrinking water.

The following flowchart is an example of the typical steps required for Category 2 watermain breaks. Where the operating authority opts to undertake Microbiological sampling, samples shall be considered distribution samples within the meaning of O. If, at any time, Contamination is evident or suspected, the break shall be reclassified as Category 2. Watermain breaks with no evident or suspected Contamination are classified as Category 1. This procedure also establishes minimum standards for record keeping, and notification to the Ministry and the local Medical Officer of Health.

Example 3 When using the slug method of chlorination, with a minimum contact time of 3 hours, the chlorine concentration shall be measured in the slug at the beginning of the disinfection process, as the slug moves through the watermain, and at the point of discharge.

Where there is no discharge point to allow for Flushing, the operating authority shall tap the watermain on the downstream side of the break and discharge from that point. When performing maintenance and repair activities as per sections 1.

When stanard the slug method of chlorination, with a minimum contact time of 3 hours, the chlorine concentration shall be measured in the slug at the beginning of the stanrard process, as the slug moves through the watermain, and at the point of discharge.

Return to normal service is contingent upon the corrective actions and sampling plan being completed to the satisfaction of the local Ministry office in consultation with local Medical Officer of Health.


Operating authorities may choose to provide notification to, or seek advice from, the local Medical Officer of Health at any time. The requirements in this section also apply to temporary watermains. Upon restoration of adwa disinfection, the system can be returned to normal service, defined as having all valves returned to normal operating position.

After business hours, the operating authority shall send an e-mail to the e-mail address specified by local Ministry office no later than 10 AM the next business day; or in the Special Cases described in sections 3. For all other types syandard cleaning e.

Disinfectant residual on stahdard post repair Flushing. If these disinfectant concentrations cannot be achieved, Flushing shall continue until the disinfectant concentration at the point of Flushing is representative of the system residual in the break area, determined by sampling upstream of the break area and downstream at the Flushing location, or by using documented benchmarks for awa area, as long as free chlorine concentrations are at least 0.

These steps also apply to the planned maintenance of watermain Appurtenances and fittings refer to section 1.

Pipe and Repair Parts disinfected? Circumferential watermain break with flow maintained until after an Air gap etandard created. Added, modified, replaced, extended; or Taken out of service for inspection, repair or other activities that may lead to Contamination, shall be disinfected before being put into service in accordance with the provisions of the AWWA C — Standard for Disinfecting Water Mains or an equivalent procedure.

Staged sampling shall be performed as follows: The operating authority shall record the duration of disinfection, as well as the standafd dose and remaining residual at the end of the contact time. Contamination is typically not suspected for circumferential breaks or small leaks where flow is maintained from the break until an Air gap is established and where the Air gap is maintained during the repair procedure.

If there is evident or suspected sewage Contamination of a watermain, in addition to the procedures in sections 3. After the completion of Flushing and restoration of secondary disinfection, at least one Microbiological sample shall be collected and submitted as soon as reasonably possible, taking into consideration laboratory working hours and transportation timeframes.

Watermain disinfection procedure |

This section does not require that all of the information be recorded on a single form:. The information shall be retained as per the record keeping requirements of Section 27 of O. Operating authorities shall develop and document operating procedures for emergency watermain repairs within their systems.


If the water level in the excavation rises such that the Air gap is not maintained after flow from the break has been discontinued, then the watermain break shall be classified as Category 2. The reporting and corrective actions of Schedule 16 and the applicable Schedule 17 or 18 of O. Flushing shall continue until the disinfectant concentration at the point of Flushing reaches at least 0.

Appendix E The following flowchart depicts the requirements for special case Contamination sewage or chemical as a result of a watermain break. Longitudinal watermain break with evident Contamination. The operating authority shall determine if flow can be maintained to the break site until the watermain is excavated.

Examples of typical steps for Category 1, 2 and for special cases are attached as Appendices C, D and E respectively.

Watermain disinfection procedure

The discharged water is deemed to be a Class II spill for the purposes of O. Discharges of flushed water are also regulated aewa Condition 4. The sampling plan shall include as a minimum taking two sets of Microbiological samples at least 24 hours apart.

The local Ministry office shall be notified as soon as reasonably possible during business hours.

The following steps must be performed for all emergency watermain repairs Category 1 and Category 2. Mechanical removal of Contaminants; Flushing into the excavation; Higher velocity flushing after repairs where practical and feasible. Flushing watermain cleaning, the requirements of section 3. The procedures are required to be followed in order to satisfy conditions imposed by the Director in a drinking water works permit.

AWWA C / AWWA C / AWWA C – Disinfection Of Water Package

The watermain may be returned to normal service defined as having all valves returned to normal operating position prior to receipt of sample results. The sampling will typically occur at the point of Flushing, and may take place from sampling ports, hydrants, blow-offs, or premise plumbing.

If planned maintenance, indicate type of planned maintenance e.

For new watermains with limited sampling points available, an alternative method of collecting Microbiological samples is called staged sampling.