Protection of the Potable Water Supply

Protection of the water supply system is paramount to the health and safety of not only the occupants of your building but also everyone else that is supplied water through a connection to the water system. Chapter 6 of the International Plumbing Code (IPC) is an example of where you will find the requirements that keep our water clean. Unfortunately, this is not a “one size fits all” approach, and understanding the nuances can save time, space, first cost, and future maintenance.  As you will see below, the process requires a complete understanding of the system and its end use.

Potable water supply systems are required to be designed, installed, and maintained in such a manner as to prevent contamination from the introduction of non-potable liquids, solids, and gasses through piping connections to the system. The various plumbing codes all have a section relating to the protection of the potable water supply, which defines the 20 or so different types of backflow preventers available and where it is permissible to use each type. These requirements vary from municipality to municipality according to the specific plumbing code that has been adopted.

These code sections describe the different types of backflow preventers and list the applicable standards for each type, which can be used to search for an appropriate backflow preventer on the various manufacturers’ websites and in their catalogs.

In general, the application of backflow preventers depends on the degree of hazard, either high or low, and the application, either backpressure or backsiphonage. There are also subparagraphs in this code section that dictate requirements depending on the type of equipment being connected to the potable water system as well as specific installation requirements for the different types of backflow preventers, such as locations and maintenance clearance. Additionally, there are subparagraphs dictating specific identification requirements for nonpotable water systems, describing signage, pipe labeling, and marking requirements.

In general, the code allows various options for the protection of connections, some as simple as including an air gap and others that are more complex and costly. The allowed methods are described and dictated throughout this section of the code.

Understanding the requirements of this section of the code and the proper selection of backflow preventers can significantly affect the installation and maintenance costs associated with the potable water system. Barton Associates has over five decades of experience designing and specifying domestic water systems.  If you have specific questions regarding the appropriate selection of backflow prevention in your facility, please contact David A. Taylor, PE, at

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