Supply hose catch-up: another viewpoint
Ronald Ludwig
Commissioner/Ex-Chief
Stony Brook (NY) Volunteer Fire Department
The criteria for selection of LDH size given by C. Bruce Edwards in “Don`t Play Supply Hose Catch-Up” (February 1995) seems to minimize some relevant information important to the majority of urban/suburban fire departments and ignores the use of steamer hydrant valves that allow for fast relay initiation without flow interruption.
First, pump design capacity is dependent on drive-train torque, which is related to vehicle acceleration and grade-climbing requirements of the purchaser. Big diesel engines for large pumpers produce high torque, which in turn mandates large pumps. Even if we don`t need them, we are going to pay for them. Many departments down-rate the stated capacity and still have 1,200- to 1,500-gpm nameplates on 1,800-gpm pumps at no significant additional expense, and they match hydrant capacity quite well. (The pump selected by the OEM had to withstand the transmission output torque.)
The majority of fire departments serving urban/suburban areas experience mostly residential fires where hydrant spacing is greater than that which exists in commercial/industrial districts but where initially required flow rates (that for which attack personnel exist) are generally in the 400- to 500-gpm range. When commercial/industrial fires demand more than 1,000 gpm, the shorter hydrant lays provide proportionally increased flow rates.
Furthermore, the additional responding pumpers, which are needed to supply required firefighters, are available to relay from the supply hydrant through carefully designed hydrant steamer valves if higher flow rates are required. (You needed the additional firefighters to handle the additional handlines anyhow.) Preplans can project the need for relay assignments of nonattack pumpers (yours or mutual aid) to satisfy exceptionally high flow requirements.
Don`t underestimate the problems created by the larger-diameter, charged LDH blocking scene access for additional critically needed ladder trucks, pumpers, and support vehicles or its susceptibility to catastrophic damage.
Although the author apparently doesn`t like relays, the utilization of lightweight LD supply/attack hose operable at 200 psi in relay allows for reduction of hose diameter.
Example: Four-inch LDH will flow 500 gpm over 800 feet if a minimum hydrant residual of 50 psi exists at that flow rate. With a 200-psi relay, 1,100 gpm can be moved through that supply line if needed, more than enough for residential applications.
The same four-inch LDH stretched 450 feet in an industrial/commercial area nominally flows 675 gpm unassisted (two big handlines or a portable monitor) and 1,500 gpm with relay; and this LDH does not block access or interfere with placement of additional apparatus.
Furthermore, by minimizing the LDH size to only what you need for attack (resulting in reduced weight per length), the potential for sprain/strain injuries diminishes when winter conditions require rapid pickup of rolled lengths to avoid freezing.
Optimizing water supply effectiveness for your needs requires complete evaluation of all pertinent factors of your protection district. In suburban districts, it appears the optimum supply hose delivers unassisted the flow needed for attack without blocking scene access. Providing for relay from the hydrant connection when exceptional need arises and scene staffing reaches required levels optimizes pumper utilization.
C. Bruce Edwards responds: I am re-minded of similar objections raised in support of traditional 212-inch supply hose when I introduced four-inch LDH to my depart-ment about 15 years ago.
Since I made high-flow-rate, short-duration Class A foam attack from the tank a standard operating procedure in 1979, resulting in rapid knockdown even of a sawmill fire, we have rarely needed hydrants–let alone relays. This SOP eliminates both supply hose spaghetti and pickup. It also saves the building.
