Which portions of the foam-water sprinkler system are not required to be flushed when the system is in service?

• A. Those portions of the system normally containing foam concentrate when the system is in service
• B. All piping downstream of the foam concentrate supply
• C. The discharge devices only
• D. The control valves only

Answer: (A)

The main idea is that flushing is used to purge debris from the water side of the system, but you must preserve the foam concentrate paths. The portions of a foam‑water system that normally contain foam concentrate when the system is in service are kept as they are and are not flushed because flushing would remove or dilute the concentrate and disturb the foam solution that would be discharged. Leaving those concentrate-containing sections intact ensures the correct foam concentration is available when the system operates.

During service or commissioning, you would typically flush the parts that do not carry concentrate to remove debris, while the concentrate-containing paths remain charged and ready to deliver foam. Flushing only downstream piping, discharge devices, or control valves would not address the need to preserve the concentrate supply and could compromise the foam operation if done in the wrong area.