Cross Connection Control

Case for containment: Backflow prevention and cross connection control implementation practices

In Colorado, water suppliers provide water to various types of customers. There are five types of customers served by public water systems: residential, multi-family, commercial, industrial and agricultural. Contamination of drinking water can occur in any supplier’s water distribution system. This potential contamination can come in the form of a cross connection. A cross connection is a connection in a plumbing system where the potable water supply is connected to a non-potable source. 

Colorado Revised Statutes 25-1-114(h) makes it unlawful to “install, maintain, or permit any cross connection between any water system supplying drinking water to the public and any pipe, plumbing fixture, or water system which contains water of a quality below the minimum general sanitary standards.” Cross connections in a drinking water supply system can be a health risk. According to the Center for Disease Control, the presence of contaminants in water can lead to adverse health effects, including gastrointestinal illness, reproductive problems, and neurological disorders. Infants, young children, pregnant women, the elderly, and people whose immune systems are compromised because of AIDS, chemotherapy, or transplant medications, may be especially susceptible to illness from some contaminants.

There are examples of different types of cross connections that suppliers may see in the table below.

Colorado cross connections to building’s internal water supply systems are generally controlled in accordance with the Colorado Plumbing Code (CPC) and the local plumbing code. Cross connections to a Public Water System (PWS) are controlled in accordance with Regulation 11. There are instances where Regulation 11 and the CPC are both applicable. This is most common for smaller PWS, such as non-community suppliers, who are located on one property and own the water supply systems.

Reduced pressure zone - Irrigation backup water supply

Regulation 11 requires that the supplier survey and evaluate their distribution system and applicable water supply systems, for potential cross connections. Specifically, the Department of Public Health and Environment requires that suppliers evaluate all non-single-family-residential (e.g. apartments) plumbing for cross connections, with the exception of connections that are controlled with an air gap or a reduced pressure zone backflow prevention assembly. These connections do not need to be evaluated. 

Uncontrolled bypass to boiler - cross connection

When discovered, water suppliers are required to implement control measures for the identified cross connections within 120 days. More information on minimum control requirements can be found in Regulation 11. Additional policy and guidance is available on the department’s Backflow Prevention and Cross Connection Control (BPCCC) webpage.

Regulation 11 allows public water systems to control a cross connection by containment or containment by isolation. When backflow prevention assemblies are installed at the service connection, this is commonly referred to as containment (figure below). Containment by isolation allows suppliers to protect the distribution system with backflow prevention assemblies, or methods installed at the location of identified cross connection within a customer’s premise plumbing and water supply system.

Example of a backflow prevention assembly installed at a location classified as containment

Courtesy of Dr. Stuart F. Asay, IAPMO

When a customer’s water supply system becomes contaminated and the service connection is not contained properly, it may create an unacceptable health risk to the public. In these incidents, the department may issue a bottled water advisory for the impacted areas. A bottled water advisory will remain in place until the supplier can demonstrate that the situation has been remedied. 

Regulation 11 does not require suppliers to control all non-single-family-residential connections with an appropriate containment assembly, and allows a supplier to protect their distribution system with the use of containment by isolation assemblies. However, many public water systems choose to implement the backflow protection and cross-connection control program in a way that all  non-single-family-residential connections must be contained to prevent any potential contamination of the distribution system. Properly implemented containment will continue to protect systems from potential waterborne disease outbreaks due to contamination from cross connection. This proven practice will protect us all from unacceptable health and or safety risks.

2018 Cross Connection Case Studies

In 2018 the department responded to three backflow contamination events due to cross connections. All three contamination events occurred on properties served by public water systems. Two of these situations were protected from potential backflow contamination at the service connections via appropriately installed, maintained and tested backflow prevention assemblies. In both cases we contacted the responsible system and confirmed their assemblies had been tested and maintained in accordance with Regulation 11. Each supplier was able to quickly provide testing reports for the containment assemblies. The properly maintained and tested containment assemblies protected their customers by preventing potential contamination in the distribution system. Because the contamination events were both contained within the customers’ water supply system, the public works systems did not have to make a public notice or take further action. The proper implementation of an adequate backflow protection and cross-connection control program was directly responsible for the protection of the public’s water supply as intended by Regulation 11.

The suppliers were able to quickly provide testing reports for the containment assemblies. The properly maintained and tested containment assemblies protected the public water systems and prevented any potential contamination of the distribution system. Since the contamination events were contained within the customer’s water supply system, the PWSs did not have to take any further action and no public notice was required of the PWSs. The supplier’s proper implementation of an adequate backflow protection and cross-connection control (BPCCC) program led to protection of the public water supply as intended by Regulation 11.

The third event happened when a supplier became aware of a suspected backflow contamination in their distribution system. When they made this discovery , they contacted the department. Their service connection was not contained, (i.e., controlled with a backflow prevention assembly). When it was confirmed that the service connection’s water supply system was contaminated, the supplier issued a bottle water advisory to 18 nearby customers because the impact to the public being served by the public work system was unknown. After the situation was remedied with  proper controls onsite, and the impacted area was flushed, the department lifted the bottled water advisory.

➽ Jorge Delgado, senior field engineer