Loss of Pressure

Distribution systems can lose pressure for various reasons that include water main break, equipment failure, loss of power, etc. Loss of system pressure endangers public health because of the high potential for the introduction of contaminants through back siphonage and through pipe joints and holes on the pipes.

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, Sustained Pressure Loss at a Public Water Supply System

The response to pressure loss and the remedial action that follows will vary depending on the cause. Based on past responses, here are a few general tips that an operator of a public water system can follow in the event of unexpected loss of pressure in the distribution system:

1. Immediately notify the EPA Region 8 Drinking Water Program in Denver (or in Helena for PWSs in Montana or in Pierre for PWSs in South Dakota or North Dakota). If our offices are closed, call the 24/7 telephone number . Be prepared to describe what happened, when, and the scope of the problem (if known).
    
2. We recommend that you notify the laboratory that you use to alert them regarding the emergency and to obtain sampling bottles, materials, and instructions.
    
3. If the area of lost pressure can be 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.
    
4. In consultation with EPA, your system may be required to issue a Tier 1 Public Notice (PN) that requires a Loss of Pressure Boil Water Advisory in accordance with the Public Notification Rule. This form is also available in MS Word Format .
    
5. EPA may also issue an Emergency Administrative Order (EAO) that mandates a Loss of Pressure Boil Water Advisory Tier 1 PN be issued. The response measures listed below and others may be required under the EAO but your system may also take these as general recommendations without an EAO:
   • Provide bottled water or other alternate water supply to customers.
   • Locate/identify and fix the problem that caused the pressure loss.
   • When system pressure is restored to normal, disinfect and flush distribution system in accordance with AWWA Standard C651.99 as necessary, or as required in the EAO, if applicable.
   • Collect and submit to the lab daily bacteriological sample from different parts of the distribution system for the number of days specified by EPA.
   • Measure and document chlorine residual results at the time and place that bacteriological samples are collected.
   • Continue to collect bacteriological samples weekly for the number of weeks specified by EPA after the daily sampling shows safe results.
   • Follow the Total Coliform Rule in response to positive sample results.

Under an EAO, the PWS will be instructed when to lift the "boil water" advisory notice and return the system to routine monitoring, if all samples test safe.

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.