By PATRICK DUNNE and SCOTT CARMONY

“Instead of asking, ‘WHAT should we do …?’ questions must be asked, ‘WHY did we start doing WHAT we’re doing in the first place, and WHAT can we do to bring our cause to life considering all the technologies and market opportunities available today?’ ”1

The quote from Simon Sinek’s book, Start With The Why, highlights what should be the fundamental question for any fire department as we evaluate our tactics. Why do we do what we do? Is the manner in which we operate on the fireground consistent with our mission? Is it consistent with the service promise we made to the public?

Our fire department has made significant changes to engine operations over the past five years. It is one of an increasing number of departments that have switched from high-pressure nozzles [100-pound-per-square-inch (psi) automatic, 80- to 90-gallon-per-minute (gpm) based on flow tests] to low-pressure (smooth bore) nozzles. While we experienced immediate improvement in suppression capacity as a result of higher fire flows, we also noted unanticipated ripple effects such as difficulties with wye operations and limitations in our water supply operations.

During an apartment fire that required multiple handlines, the engineer of the 1,500-gpm-rated attack pumper operated near cavitation while flowing approximately 1,000 gpm. The second-due engine had forward laid 300 feet from a strong hydrant that we later estimated was capable of providing in excess of 2,000 gpm. This led to an internal review to determine why we were unable to flow the capacity of our 1,500-gpm pumpers.

Historically, we’ve been a forward-lay department, first with five-inch large-diameter hose (LDH) before switching to four-inch hose in 2008. Our service area is a mix of urban, suburban, and rural with both hydranted and nonhydranted areas. Hydrant spacing, volume, and pressure vary significantly across our service area where water supply infrastructure is managed by seven separate water districts. These variables complicated our efforts to adopt a single water supply operation.

Defining the Problem

The first step in evaluating our water supply limitations was to look at our supply hose. After discussing typical failure points of modern constructed supply hose with Captain (Ret.) Dennis LeGear2, we undertook the labor-intensive project of inspecting our entire supply hose inventory for signs of delamination. We found a significant percentage of our supply hose exhibiting evidence of delamination. After removing delaminated hose, we began flow testing our supply capacity. This flow testing revealed considerably less capacity than we previously anticipated.

The methodology for the testing consisted of a series of flow tests at our training center using a hydrant system with 65-psi normal operating pressure and a capacity of 2,000 gpm per hydrant. We used a combination of our newest pumpers (with REPTO drive pumps) as well as our older front-line engines (with split-shaft midship pumps). We also used a combination of forward-lay and reverse-lay configurations, both single supply line as well as multiple supply line operations. Fire flows were calculated with a calibrated pitot gauge on smooth bore master streams.

A forward lay of 600 to 1,200 feet limits our capacity to flow approximately 500 gpm. Operationally, this translates to an inability to support a third handline (170 gpm per 1¾-inch line; 275 gpm per 2½-inch line). If a third handline is re