What should backup lines be compared to the attack line?

Backup lines are crucial in firefighting operations as they provide additional support and safety for the unit operating the primary attack line. Comparing the backup lines to the attack line means that they should either be the same size or larger. This ensures that the backup line can effectively supply water at a sufficient flow rate to support the attacking firefighters' efforts. A line of inadequate size would limit the water available, potentially compromising firefighting efforts in high-demand situations.

Additionally, the use of the same size or larger reinforces the structural integrity and capability of the firefighting operation, allowing for simultaneous operation of multiple lines if necessary. Consistency in size between the lines ensures that the firefighters can quickly switch between the lines without the need for adjustments or changes in fittings, which could cause confusion or delay in an emergency scenario.

The other choices would present challenges; a significantly larger diameter could be cumbersome and unwieldy, while minimal diameter lines would not be able to provide adequate support. Different materials could introduce reliability issues, as compatibility and performance may vary significantly. Hence, selecting backup lines to be the same size or larger than the attack line is the most effective strategy for optimal operational effectiveness and firefighter safety.