Author(s): Brian OConnor. Published on November 1, 2019.

In Compliance | NFPA 13

Why nonmetallic tubes are no longer a pipe dream for residential garages 


Material science is a complicated topic, but requirements exist that can help designers narrow down their options for choosing the piping that is appropriate for their project. To help in this process, the 2019 edition of NFPA 13, Standard for the Installation of Sprinkler Systems, includes a new provision for the use of nonmetallic piping in certain garages.

The selection of material for use in aboveground piping applications is governed by relatively straightforward requirements. NFPA 13, Table lists standards that the pipe needs to meet or exceed when used as part of a sprinkler system. This makes sense since you only want to use piping that was designed to perform in a fire event or in a range of environmental conditions. The table breaks the standards into groups for ferrous (steel), copper, brass, stainless steel, and CPVC (plastic); each has its advantages and disadvantages, as well as specific requirements for when it can be used.

Steel is the most common type of piping used in sprinkler systems. Benefits of steel include its cost-effectiveness, durability, fire resistance, and rigidity, which allows hangers to be spaced further apart per Table On the other hand, steel may not be the first choice of designers for some projects; it can be heavier than other materials, meaning it could require additional labor for installation, and it is susceptible to pitting and corrosion.

Copper and copper alloys such as brass are more corrosion-resistant than steel, which helps them stay smoother internally. This can mean less friction in the pipe, reducing the required pressure of your system. But these metals are also among the more expensive piping materials.

Nonmetallic piping such as CPVC is one of the more affordable materials. It is also flexible, has the highest corrosion resistance, and is smoother than most metals. CPVC is not as durable or fire-resistant as other materials, however, which is why it is only allowed in certain settings, such as light-hazard occupancy areas or ordinary-hazard rooms that do not exceed 400 square feet within a light-hazard occupancy.

Other factors to consider when choosing a material to use include the environmental conditions of the space where the pipe is installed. For example, some industrial occupancies could require a corrosion-resistant piping material to be installed, while an MRI machine room in a hospital would require the use of non-ferrous material. The desire to achieve a certain aesthetic appearance could also influence material selection.

In addition to previously existing NFPA 13 requirements, there is a new section ( in the 2019 edition that gives users more flexibility by permitting the use of nonmetallic piping in certain private garages within dwelling units. As mentioned, nonmetallic piping is permitted for use in light-hazard areas and in ordinary-hazard rooms not exceeding 400 square feet. Some authorities interpreted this point as permitting only metallic pipe in residential garages over 400 square feet, even if the rest of the system used CPVC. This new provision now allows nonmetallic piping to be installed in a private garage within a dwelling as long as the garage space itself does not exceed 1,000 square feet and it is protected by the appropriate wall or ceiling sheathing.

It is important to note that larger automobile parking garages should be considered ordinary-hazard group 1 occupancies. The specific allowance for using CPVC is intended to apply to smaller residential parking garages described here, but not in larger commercial garages. NFPA 13R, Standard for the Installation of Sprinkler Systems in Low-Rise Residential Occupancies, allows a garage that serves a single dwelling to be considered part of that dwelling unit, while the International Building Code limits a private garage to 1,000 square feet. This revision harmonizes NFPA 13 with NFPA 13R and the International Building Code, treating those garages as part of the dwelling unit and not as a separate occupancy subject to stricter standards.

Brian O’Connor is a fire protection engineer at NFPA. NFPA members and AHJs can use the Technical Questions tab to post queries on NFPA 13 at