Guidance For Providing Safe Drinking Water in Areas of Federal Jurisdiction - Version 1

Part 2 - Application of The Federal Framework

6.0 Distribution System Design and Maintenance

Drinking water distribution systems are made up of components that connect the water treatment plant to buildings, such as treated water reservoirs, water mains (distribution system pipes), service lines to individual buildings, backflow preventers, valves, hydrants, and, if required, pipe insulation and heating cables.⁽³⁹⁾

In general, the distribution system does not include in-home plumbing, point-of-entry or point-of-use treatment devices. However, in some situations, such as non-residential buildings and staff quarters, the plumbing may be considered part of the distribution system.

When a water source is provided by a municipality, the municipality's responsibility for the quality of the water generally ends at the curb or the point where the water enters the building's plumbing system.

When a federal facility or First Nations community uses municipal drinking water as its supply, the beginning of the facility or community's supply system marks the end of municipal responsibility. For instance, facilities in First Nations communities that receive water from the local municipality are responsible for the proper maintenance of a community water supply pipe and for monitoring the quality of water in that pipe. Should this pipe deteriorate, the water quality would suffer.

Regardless of the jurisdiction over the water source, all federal purveyors of drinking water, or, in the case of First Nations communities, Chief and Council, are responsible for ensuring the water in supply systems is tested to ensure contamination events are detected as soon as possible and can be appropriately addressed.

The department or facility's responsibilities include routine maintenance of the facility's plumbing system and analysis to determine if a change in water quality is occurring within the building ⁽⁵¹⁾. The plumbing systems in federal facilities must meet the National Plumbing Code of Canada and Standard B64.10.01.

First Nations communities are responsible for the routine maintenance of the plumbing in their homes.

A routine maintenance schedule for plumbing systems should include the following elements: inspection of the building's plumbing for cross-connections, pressure testing, flushing of water lines (when warranted) and hydrants, regular disinfection of bottled water coolers and drinking fountains, and monitoring of water quality (see Section 7.3 for further information on monitoring).

In order to keep track of the infrastructure as it was built and changes made over time, it is important to keep up-to-date drawings on hand. These drawings should include notes describing all work and observations over time.

6.1 Distribution systems, including treated water reservoirs

Distribution systems, including treated water reservoirs, should be designed to take the following into account: access by wildlife, public access, system capacity, emergency water storage (including fire flow capacity), contact time required for disinfection, the minimization or elimination of dead ends, and cross-connection controls. They should also be designed and constructed in compliance with all local or provincial by-laws and regulations and take into account best management practices.

Portions of the infrastructure that are accessible to the public and/or animals should be secured, where applicable. Treated water reservoirs should be covered, watertight and secured to prevent contamination.

When assessing the condition of water distribution systems, a two-phase approach is suggested. The first phase involves a preliminary assessment of the structural condition, hydraulic capacity, leakage and water quality on a system-wide basis using existing data. The second phase involves a more detailed investigation of specific problems based on findings of the preliminary assessment.

The most effective way to investigate the condition of a water distribution system is through regular analysis of readily available data. Table 1 in Appendix 8 summarizes the type of data that should be used to complete a preliminary assessment of each of the four common types of problems that can occur in water distribution systems. A preliminary assessment of this data should be conducted every three to five years to identify trends and to determine the need for more detailed investigations.

If the preliminary assessment indicates that a more detailed investigation is needed, experts in distribution system analysis should do the work.

Descriptions of the components of the distribution system and guidance for investigating water distribution systems are found in Appendix 8.

For more information on the disinfection of water storage facilities, see the American Water Works Association (AWWA) C650 series of manuals (found at the AWWA website under "AWWA Bookstore / AWWA Standards / Disinfection of Facilities" at url http://www.awwa.org/bookstore

6.2 Maintenance issues

If not properly maintained, many water distribution system components (including plumbing) could lead to contamination of the water supply. Corrosion is a key issue, and can cause deterioration of water distribution systems in the following ways:

Internal corrosion:

• Impaired/poor water quality due to internal corrosion of unlined metallic components, biofilm build-up and/or poor maintenance practices.
• Reduced hydraulic capacity due to internal corrosion of unlined metallic components or calcium carbonate precipitation (e.g. scaling).

External corrosion:

• High leakage rate due to external corrosion of the infrastructure, through holes in pipe barrels and/or deteriorating joints.
• Frequent breaks due to external corrosion, material degradation, poor installation practices, manufacturing defects and operating conditions.⁽⁴²⁾

A lead and copper corrosion control document is under consideration by the Federal-Provincial-Territorial Committee on Drinking Water, which would address issues related to internal corrosion.

Cross-connections can also lead to poor water quality. Devices used in the prevention of cross-connections and backflow may also deteriorate over time without regular maintenance and inspection, potentially allowing contaminants to enter the water system.

Federal facilities or First Nations communities that supply their own drinking water have to consider the distribution system from the water supply to the building or to the curb stop before the house (this may include water delivered by trucks) and then within the building to consumers. Other facilities may receive their water from municipal sources, but must still concern themselves with the distribution through the plumbing system within the building.

6.2.1 Water mains

The condition of critical water mains should be monitored to minimize failures. Critical mains are typically those which serve as a trunk line to the smaller water lines.

It is also important to monitor the condition of non-critical water mains. Failures should be "managed" to minimize operational and maintenance costs. ⁽⁴²⁾

Mains may need to be replaced, or a structural liner may need to be used, if water mains fail because of high rates of breakage or excessive leakage. If hydraulic capacity or water quality are a concern, rehabilitation might be more cost-effective than replacement.

6.2.2 Cross-connection controls

Cross-connections are physical links in the distribution system through which contaminants can enter the drinking water supply. Contaminants (eg. wastewater, detergent from a carwash) may enter the drinking water system when the pressure in a plumbed-in contaminated component is higher than that of the potable water, an event commonly called backsiphonage or backflow.

Cross-connection control programs should be in place in order to prevent contamination. Such programs include:

• Surveying established installations to rank them based on the degree of hazard that they present to the water system.
• Preparing a list of all testable backflow devices in the water system
• Assessing new construction plans for cross-connection hazards.
• Installing proper backflow preventers (backflow preventers must be testable).
• Inspecting and maintaining cross-connection control devices on an annual basis, following manufacturers' instructions.
• Training and educating staff.
• Establishing protocols for notifying the building owner or responsible party to have a particular device tested.
• Setting out the qualifications required for a person to be allowed to perform a building's cross-connection control survey.
• Instituting a tamper policy. ^{(32, 33, 39)}

6.2.3 Dead-ends and loops

Dead-ends and loops within plumbing and distribution systems result in water remaining in pipes for an extended period of time. As the water stagnates, metal concentrations may increase as a result of the pipes leaching metals into the water. Bacteriological growth in stagnant areas is also a concern.

Problems may also arise as the result of low water use or water sitting in pipes overnight (or on weekends) when no one is at the facility. As it is not possible to eliminate these times of low use, it is advisable to allow for several minutes, or other appropriate length of time, of flushing when using water the morning following weekends or other periods of low usage.⁽⁵¹⁾ Automatic flushing hydrants are available to improve water quality at the end of lines.
The appropriate flushing frequency may be determined through a sanitary survey / vulnerabilities assessment process.

As part of a sanitary survey / vulnerabilities assessment process, facility managers should work to identify any dead ends or loops in the system and measure chlorine residual. They should give special attention to dead ends and loops in flushing and monitoring schedules.

Generally speaking, it is a good idea to practice uni-directional flushing, create a written plan including valve-opening and closing sequences, and record turbidity levels and flow volumes and rates.

In northern areas, it is necessary to have looped water networks designed to ensure the continuous flow of water, which serves as a means of anti-freeze protection.

6.2.4 Recording and tracking maintenance issues

Main Breaks

Federal facilities and facilities in First Nations communities should record the location and details of water main breaks. Appendix 5 includes a form that summarizes the data that should be recorded for each break occurrence. The total number of breaks in a year should be compiled and reviewed to identify any trends.⁽⁴²⁾

Low Pressure

The distribution system should be pressure-tested on a regular basis to ensure that flow pressure conforms to section 6.3 of the most recent version of the National Plumbing Code of Canada.⁽⁹⁾

Low-pressure complaints must be recorded. If the number of complaints increases over time, it may suggest that the hydraulic capacity of the system is deteriorating. A visual or camera inspection of the interior of water mains can help indicate the degree of tuberculation and encrustation.

The inferior condition can also be determined by visually inspecting the water when a water main is flushed.⁽⁴²⁾

A complete cross-connection control program includes training and education for staff. Employees who will administer the program will need competencies in the use of backflow testers, surveys and device repair.⁽³²⁾ Each department's training plan must address these needs.

6.2.5 Routine flushing of the plumbing system

Routine maintenance must include flushing of water lines within a building. A minimum flushing regimen should be put into place, with flushing frequency based on the sanitary survey and vulnerabilities assessment. At minimum, it is suggested that water be flushed through the lines every 6 to 8 weeks in all inactive areas of the plumbing system (e.g., water fountains that are used infrequently, areas with dead-ends or loops). The entire system should be flushed once a year.⁽²⁶⁾ The sanitary survey and vulnerabilities assessment may identify site-specific problems that require more, or less, frequent attention.

6.2.6 Drinking water fountains

Drinking water fountains must be disinfected to ensure contamination does not occur at the spigot. Fountains should be disinfected a minimum of once every two months and at an increased frequency if heavily used.⁽⁵¹⁾ They should also be maintained according to the manufacturer's recommendations.

6.2.7 Water quality complaints

A preliminary assessment of the water quality in a distribution system can be completed using routine water quality monitoring data, complemented by water quality complaint records. The water quality complaint records should be recorded and tracked in a manner similar to that for low-pressure complaints or breaks. Water quality complaints related to construction and maintenance activities (e.g., flushing, repairs, new construction) should be excluded from the analysis to reflect the condition of the system properly but should be reviewed to determine if operational changes are necessary.

On-going analysis of water quality data will indicate if the water quality is changing through the distribution system, both spatially and over time. Low chlorine residuals in some parts of a system, in combination with increased colour, high turbidity, increased iron, increased HPC, drops in pressure or flow, may demonstrate that the mains in these areas are deteriorating. Low chlorine residuals could also indicate deteriorating water quality. Similarly, the concentration of iron in the water may denote the degree of internal corrosion of unlined mains.⁽⁴²⁾

6.3 Chlorine/chloramine residuals

Disinfection is critical to ensuring the safety of the drinking water supply in the treatment plant. In addition to disinfection, chlorine (or chloramine) is used in residual amounts to ensure continued disinfection throughout the distribution system and to protect the water from re-contamination.

Tests of chlorine residuals at the drinking water treatment plant and in the distribution system are needed to determine chlorine dosage levels and to monitor water quality

In a drinking water distribution system, a disinfection residual of at least 1.0 mg/L of total chlorine or 0.2 mg/L free chlorine must be present in the water at all times. Other disinfection processes can be used in the treatment plant (e.g. ultraviolet disinfection), but in these cases a chlorine residual must still be maintained in the drinking water distribution system.

In the case of a groundwater source that serves very few individuals and has little or no distribution system, no chlorination is needed.

More information on disinfection, including groundwater issues, is found in Section 4.3.

6.4 Special circumstances

6.4.1 Alternative sources of drinking water

On a temporary basis, departments may need to provide an alternative source of drinking water to consumers:

• If the water supply has become contaminated or is otherwise considered unacceptable,
• If there are problems in the distribution system or plumbing, or
• Simply for convenience.

This water could be boiled and filtered or departments could choose to provide bottled water. Bottled water also includes water coolers and/or dispensers.

Although bottled water may be safe when it is delivered, precautions should be taken to ensure it does not become contaminated at the dispenser.

Canadian missions in foreign countries may also use bottled water. However, water bottled in other countries is not necessarily safe. In foreign jurisdictions, initial bacteriological testing of bottled water should be conducted to ensure a safe supply. A total of five samples from each brand of bottled water is recommended to test for E.coli and total coliforms. Pseudomonas aeruginosa could be measured as well, as an indicator of whether the product has been manufactured under Good Manufacturing Practices. Once a bottled water supplier is selected, periodic sampling should be conducted to ensure the continued safety of the supply.⁽²⁴⁾

See Appendix 4 for details on how to maintain water coolers and dispensers.

6.4.2 Trucked (hauled) water

Remote locations, or those that do not have easy access to a reliable drinking water source, may have to rely on drinking water hauled to the site. Hauled water to be used as a drinking water supply must meet the Guidelines for Canadian Drinking Water Quality.⁶ The original source of the hauled water should be a water system whose treatment provides a disinfection residual before being delivered to the truck.^(1,52)

Contamination issues with trucked water may arise as a result of the increased handling of the water and storage within a reservoir tank at the point where the water is dropped off. Testing the quality of trucked water should include sampling at the filling point. Water in the truck should be sampled once per day.⁽⁴³⁾

The sanitary condition of the transportation equipment is very important. The tank or container used to carry potable water and pumps, hoses and other equipment used in the supply or delivery of the potable water should be maintained and operated in a clean and sanitary condition ⁽⁵⁰⁾, and must be free of contaminants. The tank/container must not be used to transport other materials likely to contaminate that water (e.g., milk) ^(1,52), and must not have been used previously to transport a noxious, hazardous or toxic substance.

The container should be constructed of materials that meet NSF/ANSI Standard 61 for Drinking Water Additives (Unintentional Additives - Drinking Water System Components - Health Effects), and should allow easy access for cleaning. The tank/container used to transport the water should be disinfected on at least a weekly basis. When the container is filled or emptied, precautions must be in place to prevent backflow or backsiphonage (e.g., through an air gap or double-check valve assembly).

For information on disinfection of water storage containers, see the American Water Works Association (AWWA) C650 series of manuals (found at the AWWA website under "AWWA Bookstore / AWWA Standards / Disinfection of Facilities" at url http://www.awwa.org/bookstore

The outlet connections at filling points must be constructed and protected so that contaminants cannot enter the water supply and so their nozzles are kept free of ice build-up during the winter. These inlets should be closed except when filling or cleaning the tank. Receiving tanks or cisterns should also be maintained in a clean and sanitary condition and should not be used for any other purpose.^(1,52) Receiving tanks or cisterns must be cleaned and disinfected before they are put into use, and when the system or any of its parts are dismantled for repair, maintenance or replacement.^(43,55) Cisterns should be monitored for bacteriological parameters at least 4 times per year.⁽²⁸⁾

A disinfection residual of at least 1.0 mg/L of total chlorine or 0.2 mg/L free chlorine must be present in the water at the time of delivery. The quantity of free chlorine residual should be measured once per day, in a water sample collected at the outlet of the tank truck. All data should be recorded in a register containing the data and results of the measurements and the name of the person who took them.^(1,52)

For an example of guidelines for ensuring the safety of trucked water, see the Quebec government's regulations in this area.

⁶ No federal regulations relate to hauling potable water. Some provinces/territories have specific requirements for trucked water, and the guidance in this document is based mainly on these guidelines/ standards, as well as on additional information from Indian and Northern Affairs Canada and the Department of National Defence.