What does a Combination System refer to in NFPA 13R?

• A. Systems using several manufacturers.
• B. Systems using both steel and nonmetallic fittings.
• C. Systems requiring exclusive use of steel piping.
• D. Systems that operate without water supply.

Answer: (B)

In NFPA 13R, a combination system means the sprinkler system uses both steel piping and nonmetallic piping/fittings within the same installation. This approach is allowed under certain conditions to balance cost and ease of installation while still meeting performance and protection requirements. The idea is about mixing materials, not about meeting other criteria.

So this is the best answer because it directly captures the meaning of “combination” as combining different piping materials in one system. The other options describe considerations that aren’t what the term refers to—using multiple manufacturers, requiring only steel, or operating without water supply.