Deficiency Classification for Drinking Water and Other, Non-recreational Waterborne Disease Outbreaks

Waterborne disease outbreaks are assigned one or more deficiency categories based on available data. The deficiencies provide information about how the water became contaminated, water system characteristics, and factors leading to waterborne disease outbreaks.

Deficiencies Assigned to Outbreaks Associated with Drinking Water, Other Water, and Unknown Water Exposures

  • Contamination of drinking water (i.e., public, individual, or bottled water systems) at/in the water source, treatment facility, or distribution system*
    1. Untreated surface water
    2. Untreated ground water
    3. Treatment deficiency (e.g., temporary interruption of disinfection, chronically inadequate disinfection, or inadequate or no filtration)
    4. Distribution system deficiency, including storage (e.g., cross-connection, backflow, contamination of water mains during construction or repair)
    5. Current treatment processes not expected to remove a chemical contaminant (e.g.,pesticide contamination of ground water treated with disinfection only)
      1. Surface water
      2. Ground water
  • Contamination of water at points not under the jurisdiction of a water utility or at the point of use†
    1. Legionella spp. in water system
      1. Drinking water (i.e., public, individual, or bottled water systems)
      2. Other non-recreational water (e.g., cooling/industrial, water reuse, irrigation, occupational, decorative/display, includes water consumed from sources such as back-country streams)
      3. Unknown water use (i.e., the intended purpose or use of the water is unknown or the water exposure category could not be determined)
    2. Plumbing system deficiency after the water meter or property line (e.g., cross-connection, backflow, or corrosion products)
    3. Deficiency in building/home-specific water treatment after the water meter or property line
    4. Deficiency or contamination of equipment using or distributing water (e.g., drink-mix machines)
    5. Contamination or treatment deficiency during commercial bottling
    6. Contamination during shipping, hauling, or storage
      1. Drinking water – tap water
      2. Drinking – commercially-bottled water
    7. Contamination at point of use
      1. Tap
      2. Hose
      3. Commercially-bottled water
      4. Container, bottle, or pitcher
      5. Unknown
    8. Drinking or contact with other non-recreational water
  • Unknown/Insufficient Information
    1. Unknown/Insufficient information
      1. Drinking water – tap water
      2. Drinking water – commercially-bottled water
      3. Other non-recreational water
      4. Unknown water use

*For a community water system, the distribution system refers to the pipes and storage infrastructure under the jurisdiction of the water utility prior to the water meter or property line (if the system is not metered). For noncommunity and nonpublic individual water systems, the distribution system refers to the pipes and storage infrastructure before entry into a building or house.

† Contamination of drinking water and deficiencies occurring in plumbing and pipes that are not part of the distribution system as defined previously. For community systems, this means occurring after the water meter or outside the jurisdiction of a water utility; for noncommunity and nonpublic systems, this means occurring within the building or house (e.g., in a service line leading to a house or building, in the plumbing inside a house or building, during shipping or hauling, during storage other than in the distribution system, or at point of use).