When should underground piping supplying the system be flushed?

• A. Underground piping should be flushed in accordance with NFPA 24
• B. Underground piping should be flushed in accordance with NFPA 25
• C. Never flush underground piping
• D. Only after first use

Answer: (A)

Flushing underground piping is part of preparing the system during installation to remove debris, sediment, and any contaminants that can cause blockages or impurities once the system starts up. NFPA 24 governs the installation of underground standpipe piping and specifies the procedures for flushing and purging, including acceptance testing, to ensure the line is clean before being put into service. That’s why the correct choice is to flush according to NFPA 24. NFPA 25, by contrast, covers maintenance and testing after installation, not the initial flushing requirements. Flushing after first use would delay addressing debris that could affect operation, so it’s not the correct approach.