by Bill Kleiman, The Nature Conservancy, Nachusa Grasslands
At Nachusa Grasslands we use several vehicle mounted water sprayers on our fires. We call them “pumper units”. Photo above is a crew about to start their test ignition. You don’t see backpack water sprayers as most crew are assigned to a pumper unit.
The pumps we use are piston pumps because they use a small amount of water per minute and produce a high pressure. These work well for our grass and leaf litter fires and are common in the Midwest.
Centrifugal pumps are the standard on wildfire crews you see across the nation. Centrifugal pumps typically produce modest pressure, and can pump a lot of gallons per minute. This is good in that you may knock down an escaping fire with all that water output, and bad in that you may run out of water before that escape is extinguished.
Below is one of our units. Note rake strapped at an angle such that it does not hit you in the head when you start the pump motor. Our name is on the rake so we get it back at the end of the day. The hose is yellow so you see it in the grass. The hose is a narrow diameter so it is light weight to maneuver easily. The drip torch holders are made from wood painted black. The laundry detergent bottle in the box is filled with Class A foam. “Add two caps of foam” says the print on the side of the tank fill. And it all fits in the bed with the tailgate up. The tank is 70 gallons which is about ten gallons too heavy.
Our water tender is a 425 gallon tank with a high flow centrifugal pump mounted in a truck. It is to fill all the other pumpers in the field and carry extra tools.
I wrote up a short summary of pumper units designs: https://www.illinoisprescribedfirecouncil.org/uploads/1/0/5/8/105892833/pumper_unit_design_suggestions_2019_bk.pdf