How many additional lines can be opened when the hydrant static pressure on the pump intake gauge is 80 psi and the residual pressure drops to 70 psi while flowing several attack lines totaling 300 gallons/min?

To determine how many additional lines can be opened under the given conditions, we must first analyze the available pressure. The hydrant static pressure indicates that initially, the pump can draw water at 80 psi. When water is flowing through the existing lines, the residual pressure drops to 70 psi.

The difference between static and residual pressures indicates the available pressure that can still supply more lines. To find the pressure available for additional lines, we can subtract the residual pressure from the static pressure:

80 psi (static) - 70 psi (residual) = 10 psi.

This 10 psi is the critical pressure drop available to support additional lines. The number of additional lines that can be opened depends on the flow requirements of each line, which typically range from 100 to 150 gallons per minute when flowing at a manageable pressure.

Given that the total current flow is 300 gallons per minute, if we consider each additional line flowing 100 gallons per minute, we can afford to open additional lines until the pressure drops below acceptable levels for safe operation.

In this scenario, with 10 psi available, it allows for a greater number of flow additions without dropping the pressure too low to maintain valid hydrant performance. Therefore, under the pressure conditions