Which interlock configuration is used by combined dry-pipe pre-action systems?

Which interlock configuration is used by combined dry-pipe pre-action systems?

• A. Single interlock
• B. Double interlock
• C. Triple interlock
• D. Quadruple interlock

Answer: (B)

Water release in combined dry-pipe pre-action systems is controlled by two independent gates that must both operate before any water reaches the sprinklers. The first gate responds to an automatic detection/alarm signal and triggers the pre-action valve, opening the path to fill the dry pipe with water. The second gate is the sprinkler actuation, which actually allows the water to flow from the pipe to the sprinkler heads. This two-step sequence—two separate conditions being met—provides a safety margin against false or accidental releases. A single interlock would release on one event, which is riskier for dry-pipe/pre-action setups; having two interlocks (double interlock) is standard practice to ensure water only enters the system when a fire is both detected and confirmed by sprinkler activation. More complex interlock counts (triple, quadruple) aren’t typical for this configuration.

Water release in combined dry-pipe pre-action systems is controlled by two independent gates that must both operate before any water reaches the sprinklers. The first gate responds to an automatic detection/alarm signal and triggers the pre-action valve, opening the path to fill the dry pipe with water. The second gate is the sprinkler actuation, which actually allows the water to flow from the pipe to the sprinkler heads. This two-step sequence—two separate conditions being met—provides a safety margin against false or accidental releases. A single interlock would release on one event, which is riskier for dry-pipe/pre-action setups; having two interlocks (double interlock) is standard practice to ensure water only enters the system when a fire is both detected and confirmed by sprinkler activation. More complex interlock counts (triple, quadruple) aren’t typical for this configuration.