Firefighting 101                                                         by:  Dan Howell

Water Supply

Fire extinguishment is a basic and fundamental operation of the fire service. In order for this extinguishment to effectively take place, the fire must be attacked with an adequate amount of water that is capable of overwhelming the amount of heat being generated by the fire. I t is the challenge of the fire service to supply and deliver this required flow. As a result, water supply is a critical and essential part of every fire incident. Despite its importance however, an effective water supply is often neglected until it is too late, resulting in fires that escape the capabilities of initial arriving units and leading to greater property loss and increased dangers to firefighters.

          Water supply begins with the initial size-up and upon arrival, quick decisions must be made about the adequate amount of water needed to quickly knockdown the fire. The easiest way to do this without resorting to formulas that are gross approximations at best, is to know how much each attack line and master stream can flow and how much fire each can extinguish. This information can only be determined with experience and training, but once obtained, the correct amount of water necessary for extinguishment can be determined. Add up the amount of water each line is capable of flowing per minute and this is the amount of water you want to be able to supply. If a smaller amount of water is supplied, then a rapid knockdown is mandatory, if this does not occur, then water supplies will be depleted. Remember, when determining the amount of water to initially attack the fire with, a whole lot of water real quick is better than a small amount over a long period of time! Even with limited water, high flow attacks applied properly are the only attacks that have any hope in stopping a large and fast moving fire. Low flow attacks that gradually apply water to the fire only empty tanks and leave the fire burning.

          Not only must the water supply provide for an adequate flow, it must also be continuous. A continuous water supply is mandatory to ensure that fire attack operations will not have to cease or conserve, events that lead to prolonged incidents and increasing dangers to firefighters. For a continuous water supply to exist, the best possible water source must be determined. This can only be accomplished during preplanning and training. It is highly likely that this water source cannot be fully utilized by the responding department alone. As a result, the responding department must have the necessary mutual-aid in route early to maximize the full potential of the selected water source and the water supply generated. Furthermore, the department should not be afraid to initiate water supply plans often, even if they may not always be necessary, some day they will make a difference.

          A third characteristic of an effective water supply is an efficient water supply. Water supply operations will only be efficient if supported with departmental training. Efficient water supplies are more professional and far safer than operations that are hurried and unorganized. The opportunities to improve efficiency are determined by the basic form of the water supply, tanker shuttles or hose lays.

          Hose lays can be used if hydrants or static sources are available. A big advantage to hose lays is that they reduce the number of trucks shuttling which vastly improves safety and frees up more firefighters for fireground operations. Disadvantages include possible long set-up times and extensive stretches of hose on the ground. Also, an adequate number of pumpers must be available to get the water from the source to the scene. It must also be ensured that the source can supply the hose lay or relay. Again, this is information that can only be determined before the fire. Hydrants should be flow tested and the volume of static sources determined as accurately as possible. When determining what size hose to lay, remember that large diameter hose is far superior to smaller sized hose. Another factor to consider when connecting to hydrants and to trucks is to use the largest intakes or discharges available. On hydrants the steamer connection can be as much as 30% more effective than a 2.5” discharge. At the pumper, steamer connections have only a fraction of the friction loss compared to a 2.5” intake. In low-pressure situations, these losses can be significant.

         In rural areas, hydrants are often an unavailable luxury and static water sources usually are not close enough to the fire to allow for a practical relay. As a result, the tanker shuttle will be the method selected to provide the necessary water supply. Tanker shuttles have the disadvantage of keeping trucks in continuous motion, which increases the chances of disastrous accidents and commits valuable personnel to driving the tankers. In addition, tanker shuttles, by nature, are very inefficient. With proper training and good preplanning of all possible water sources, tanker shuttles can be highly effective methods of delivering water to the fire scene. In order for tanker shuttles to be efficient they must be initiated early by requesting adequate resources and assigning a water supply officer who can get the shuttle established and organized. A good dumpsite must be arranged on scene with drop tanks positioned so that tankers can unload easy. If this is not possible lay lines to the drop tanks and then pump the water in from a position where tankers can maneuver easily. A nurse tanker could also be used to pump the water from the drop tanks to the attack pumper. At the fill site, the use of a pumper connected to the water source is highly recommended since it will be able to fill many tankers at once. The goal of good dump and fill sites is to reduced tanker turn-around time and prevent tankers from having to wait in line. The crucial point of water shuttles is to remember that time is water, and that the most time to be lost or gained is at the fill and dump sites.