Your engine is supplying the FDC at a high-rise building with dual 3" lines, 50' in length. What is the friction loss for two standard high-rise packs on the 7th floor and one on the 6th floor?

To determine the friction loss in this scenario, it is important to refer to the friction loss formulas applicable to the hose diameter and the conditions presented. For 3-inch diameter hose, a common rule of thumb for calculating friction loss is to use the formula:

Friction loss (in psi) = (length of hose in feet ÷ 100) × (GPM ÷ 100)².

In this scenario, the total length of hose supplying the standpipe to the 7th and 6th floors amounts to 100 feet when you combine the two lines of 50 feet each.

Since each high-rise pack is typically rated at around 150 GPM, applying this flow rate into the formula provides a friction loss of:

1. For the first line on the 7th floor:

   • Length: 50 feet
   • GPM: 150
   • Friction loss = (50 ÷ 100) × (150 ÷ 100)² = 0.5 × 2.25 = 1.125 psi.

   Because it is on the 7th floor, this is doubled due to the two packs:

   Total friction loss for two packs on the