When a pumper is supplying four lines of 2-1/2" hose, each equipped with a 250 gpm fog nozzle at 100 psi, the pump discharge pressure required is approximately what?

To determine the required pump discharge pressure when supplying four lines of 2-1/2" hose with each equipped with a 250 gpm fog nozzle at an operating pressure of 100 psi, we can follow a procedure that factors in both the necessary nozzle pressure and the friction loss in the hoses.

The first step is to recognize that each fog nozzle requires 100 psi for operation. Since there are four lines, the total pressure required for the nozzles alone sums to 100 psi for each nozzle; thus, the nozzle pressure remains at 100 psi regardless of the number of lines.

Next, we need to consider the friction loss in the hoses. For 2-1/2” hose, the friction loss can be estimated using a formula generally accepted in fire service, which specifies approximately 10 psi loss per 100 feet of hose at 250 gpm. However, since the exact lengths of hoses are not given in the question, we can outline a common scenario—for instance, if each line is 200 feet, the friction loss would be 20 psi per line (2 x 10 psi), which then needs to be multiplied by the number of lines.

Calculating for four lines:

• If each line is