Hydraulics at Your Fingertips

By Jeff Welle

The Hydraulics 4 Jakes (H4J) pump operator's system offers a simple, comprehensive approach to calculating fireground hydraulics. The International Fire Service Training Association's (IFSTA) friction loss equation is the firefighter's benchmark for pump proficiency. H4J is based on the IFSTA formulaic approach to pump operations and correlates remarkably well with what would be derived using the IFSTA friction loss equation, C × Q² × L, where C is the coefficient of friction, Q is the flow in gallons per minute divided by 100, and L is hose length divided by 100. The H4J system provides a simple and reliable tool that will provide accurate fireground hydraulic calculations.

There is a limited range of fire service nozzle sizes, required flow rates, and standard nozzle pressures (SNP). A nozzle operated at the SNP will produce a reasonably predictable quantity of water. H4J uses this general nozzle flow rate predictability to provide sequential, tactically relevant flow rates. H4J's rounded flow rates do not represent the exact quantity of water flowing at any point within the evolution; they are based on anticipated SNP nozzle flow rates and their supply. The system enhances firefighter confidence in operating integrated hose configurations and achieves a flow rate very near the desired nozzle requirement or supply need.

The H4J flow rates are based on standard stated fog nozzle flow requirements and the solid stream IFSTA equation 29.7 × D² × square root of NP. The IFSTA solid-stream equation was used with the various tip sizes operated at the SNP and the results were simply rounded, providing anticipated nozzle requirements that are tactically relevant and easy to remember.

As a distribution device's flow rate is achieved within any size hose, the hose will have a reasonably predictable resistance to the water flowing within it, known as friction loss (FL). The friction loss calculation method used by H4J is universally applicable to the different sizes and categories of hose. The underlying variations in the flow capabilities of different hose sizes allows H4J to offer a simple universal friction loss number sequence that is used to operate multiple sizes of hose. The universal H4J friction loss number sequence identifies the corresponding flow rate's rounded friction loss per 100 feet in a specific size hose at the provided H4J flow rate. The H4J friction loss number sequence will provide near benchmark hydraulic calculations for the four sizes of medium diameter hose (MDH) and large diameter hose (2 1/2-, three-, four-, and five-inch). The two sizes of attack hose (1 1/2- and 1 3/4-inch) share another easy-to-remember friction loss number sequence.

H4J will provide flow rates for every industry standard nozzle's SNP flow requirement and the combined requirements of multiple nozzles operating simultaneously. The H4J attack hose flow rates are nozzle-requirement specific. The combined flows of dual attack lines supplied by MDH are reflected in H4J's MDH flows. All single-line MDH nozzle flow rates are identified. Flows for dual and tri-line MDH supplying a master stream or appliance are easily determined by selecting a tip size/nozzle flow/supply need and applying equally divided flow rates. Operating in between the H4J flow rates is obvious, and the two sizes of MDH offer 18 different gpm flows to meet the multiple nozzle/supply needs of the fireground. H4J will operate single, dual, wyed, and multiple-line configurations. The H4J flow rates are rounded, sequential, hose category integrated, and operationally significant.

Virtually every flow rate incorporated into the H4J system has a tactical application and some flow rates offer single, dual, and multiple-line operational options. The firefighter correlates the nozzle requirement and simply adds the rounded friction loss number by the length of the hose evolution.

H4J uses the firefighter's hand as a reference point (Figure 1). Place the left hand forward, thumb to the left. The numbers at the base of each finger are rounded, sequential, and operationally significant nozzle/supply oriented flow rates. At the top of each finger is the H4J universal friction loss number sequence. The sequential H4J flow rates will have an associated friction loss, which is easily identified by correlating the universal friction loss sequence with the desired flow.

View the 2 1/2-inch hose flow rates used by H4J and identify the handline nozzle applications of 200, 250, 300, and 350 gpm. Supplying a master stream device with dual 2 1/2-inch lines is easily accomplished with the H4J flow rates of 250, 300, 400, or 500 gpm. The H4J MDH flow rates will also accomplish any dual attack/MDH nozzle combination. Multiple line strategies are easily accomplished with equally divided flow rates. The firefighter must correlate the nozzle requirement with the predetermined flow rates and universal friction loss number sequence used by H4J. The system will be accurate to the IFSTA equation, and is designed to be simple, fast, and globally fireground comprehensive.

Example: 200-foot, 2 1/2-inch hose; 350-gpm fog nozzle; and SNP of 100 psi.

IFSTA: 2 × 3.5 × 3.5 ×2 = 49

49 + 100 = 149 psi

H4J: 25 + 25 + 100 = 150 psi


Figure 1. Hydraulics 4 Jakes System

Jeff Welle is a career paramedic, firefighter, and registered nurse. E-mail: info@hydraulics4jakes.com.

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