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Loss of Pressure in Drinking Water Systems in Wyoming and on Tribal Lands in EPA Region 8

Loss of Pressure

Distribution systems can lose pressure for various reasons that include water main breaks, equipment failures, losses of power, etc. Loss of pressure in a drinking water distribution system may cause a net movement of water from outside the pipe to the inside through cracks, breaks, or joints in the distribution system. Backsiphonage is also a condition resulting from low or no pressure. Such system failures carry a high potential for fecal contamination or other disease-causing organisms to enter a distribution system and can cause serious health concerns for people who drink the contaminated water. Pressure loss is defined as a distribution system pressure of less than twenty (20) pounds per square inch (psi).

Measures to Take in the Event of Partial or Full Pressure Loss at a Public Water Supply System

The response to pressure loss and the remedial action that follows will vary depending on the situation. However, listed below are the actions that an operator should take in the event of a loss of pressure in the distribution system that is likely to last longer than one hour:

  1. If the area of lost pressure can be valved off and contained, you should isolate this area from the rest of the system. This may limit the degree of contamination and the number of service connections affected by the loss of pressure.
  2. Immediately notify the EPA Region 8 Drinking Water Program.
    • Public Water Systems (PWS) in Wyoming: call 303-312-6010
    • Tribal PWS in Utah, Wyoming, or Colorado: call 406-457-5009
    • Tribal PWS in Montana: call 406-457-5009
    • Tribal PWS in North Dakota, South Dakota: call 605-945-1192
    • If outside of normal business hours, call the 24/7 number: 303-312-6327
    • Be prepared to describe: what happened, when, where, and the scope of the problem (if known).
  3. We recommend that you notify the laboratory that you use to alert them regarding the emergency and to obtain bacteriological sampling bottles, materials, and instructions (for taking Special bacteriological samples).
  4. In order to protect your customers, immediately issue a Tier 1 Public Notice (PN) that includes a Loss of Pressure Boil Water Advisory. This form is also available in MS Word Format. If boiling the water is a hardship for customers, consider providing bottled water or another alternate water supply to customers.
  5. Locate/identify and fix the problem that caused the pressure loss.
  6. When system pressure is restored to normal, disinfect and flush the affected distribution system in accordance with AWWA Standard C651.99 as necessary.
  7. After the excess chlorine has been flushed out of the water supply, collect and submit to the lab Total Coliform (TC) bacteriological samples from both upstream and downstream of the affected area of the distribution system. Maintain the boil water advisory until two consecutive days of “safe” TC samples have been collected, or until EPA notifies you that the boil order can be lifted. These samples should be designated/marked as “special” samples on the lab slip if they are not intended to be used as routine samples under the Revised Total Coliform Rule.
  8. Measure and document chlorine residual results at the time and place that bacteriological samples are collected. Chlorine residual in samples will need to return to normal levels prior to considering returning the system to normal operations.

The EPA may issue an Emergency Administrative Order (EAO) for incidents that can result in contamination in or near a public water system that may pose an “imminent and substantial” endangerment to human health. If an EAO is issued to the system owner, the operator must follow all the requirements (e.g., issue a Tier 1 Public Notice, complete corrective actions, disinfect and flush the system, collect special total coliform samples) listed within it.

Prepare for the Unexpected

Every water utility should have an Emergency Response Plan (ERP) that addresses emergencies, such as loss of pressure, with a checklist of steps to take. The ERP must be exercised periodically in order for all utility personnel to be familiar with it. Regular maintenance and timely implementation of sanitary survey recommendations may also help in preventing or reducing emergencies.