Group B Public Water Systems - Pressure


Losing Water Pressure

What happens if I lose pressure in my system?

Events causing a loss in water pressure may be planned or unplanned. For example, system operators may plan to reduce pressure when they install, replace, or repair water lines. Broken water mains, a failed pumping system, power outages, leaking storage reservoirs, and excessive demand can cause unplanned pressure loss.

Use this public notice template (Word) to notify your customers of a water outage or loss of pressure in your water system.

Should I be concerned about losing water pressure in my system?

Yes. Pressure loss can be a serious threat to public health. A reduction or loss of pressure in the distribution system can result in backflow, allowing contaminants to enter drinking water through unprotected cross-connections. Backflow is a reverse of normal water flow due to back pressure or back siphonage that occurs when the pressure of a polluted source exceeds the pressure in the distribution system. Backflow incidents have caused illness, injury and, in some cases, death.

What should I do if my system loses pressure?

Immediately take the following steps to ensure the safety of your customers:

  1. Find the cause of the problem and restore pressure. Your first priority is restoring water pressure and maintaining the ability to fight fires.
  2. Flush the lines. Customers face greater risk of consuming contaminated drinking water after a pressure-loss event. Flush the lines to reduce the risk and cleanse the system of contaminants. Follow general industry standards for flushing the system.
  3. Disinfect the system. Disinfection is a preventive measure to protect the water system. However, you must notify your customers first. For guidance, see Emergency Disinfection of Small Systems, DOH 331-242 (PDF).
  4. Collect Samples. After you restore normal operating pressure:
  • Collect at least two coliform samples from your system.
  • Review the results of the sampling.
  • Advise your customers about the status of their drinking water supply.

For a list of certified labs, visit the state Department of Ecology. Under "Location," select your state, city, and county. Scroll down and click on "Show results." Click on the name of a lab to see the tests it performs. Call the lab to make sure it's accredited to analyze for coliform bacteria.

How can I prevent backflow?

The best way to prevent backflow is by developing and implementing a cross-connection control program. For guidance, see Cross-Connection Control for Group B Systems.

How do I know if backflow occurred?

Most pressure-loss events are obvious; however, there are times when you may not know an event occurred. These events can be a serious threat to public health because of the ever-present link to possible contamination through a cross-connection.

Indications of a backflow incident include:

  • Discolored or unusual looking water. Investigate any abnormal appearances of water, such as unusual color, soapy, foamy, or oily water. Discolored water can also be caused by increased flows in pipes or changes in normal pipe flows that disturb sediments in the distribution system. Investigate all reports of colored water.
  • Inconsistent chlorine residuals throughout the distribution system. Chlorine in the distribution system reacts with many different substances, including possible backflow contaminants. Low or zero chlorine residuals in the distribution system following a loss of pressure event could be a sign that chlorine is reacting with substances not normally found.
  • Taste and odor complaints. If there are taste and odor complaints after a low-pressure event, evaluate the nature of the complaints and call us for technical assistance. Detectable differences in taste and odor could indicate a backflow incident occurred. The human nose and taste buds are extremely sensitive and can detect some contaminants in water at extremely low concentrations.