Article and photos by Paul Shapiro
SMALL-GPM WATER SUPPLY
The small- gpm fires statistically do fine with a basic supply line evolution from the hydrant. However, in the rare situation that the initial supply line can’t produce the required flow, you must have a plan to get more water. This type of operation is called “supplemental pumping,” a term used for operations that bring in an additional water supply to an engine that has its initial water supply and is running out. It is important to delegate this task to a unit from the start before a problem arises, not after. It can be as simple as having one operator with an engine set in staging ready to lay that second supply line to the pumping engine.
Many departments use a hydrant assist valve to increase the flow to an existing water supply. This appliance is preconnected to the end of the supply line on the unit and is attached to the hydrant when a line is laid. When the hydrant is turned on, the water flows through the valve and into the supply line directly to the receiving pump as in a normal operation. If more water is needed from the hydrant, a second pumper can connect into the valve, divert the water through its pump, and boost the flow through the supply line without shutting the hydrant down.
LARGE-FLOW WATER SUPPLY
During the initial size-up of a large-volume fire, one of the tasks that needs to be addressed is setting up secondary water supplies to the initial attacking units. Again, as with the small-fire operations, assign operators and their units to develop the evolutions needed. The only difference between the large- and small-water supplies is that the units should immediately deploy the secondary water supply evolutions. There’s that proactive word again. Don’t wait for a water supply problem to arise; set up that backup system in anticipation of having issues, because on the big one, there is a good chance it will. Now is the time to make a maximum effort to get as much water as possible to the fireground.
Supplemental pumping is the key ingredient for a large-flow water delivery operation, especially when distant hydrants are needed to supply engines already operating and in need of more water. Often at large fires, the first few units will lay from hydrants close to the fire and spot in the area needed. This is when a water supply problem usually starts. These units have everything they need to attack the fire. They have the personnel, correct apparatus placement, and proper deployment of the discharge evolutions. Since these units brought in hydrants close to the fireground, the hydrant grid system in that area is becoming depleted of water or pressure.
(6) An alternative to the dual-pump operation uses a large gated manifold at the receiving end of the relay to distribute the water to multiple engines on the fireground.
Figure 1. This illustration shows a looped supply line evolution. Several engines are connected to five hydrants, sharing water using dual-pump operations.