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= Waterax MARK-3 = The Waterax Mark-3 is a lightweight, high-pressure centrifugal fire pump designed for direct wildfire suppression. After its conception in 1964 by WAJAX Ltd. (later known as Waterax), the pump became widely adopted as the standard for lightweight, portable wildland fire suppression pumps by forestry agencies worldwide.

Specifications
The Mark-3 consists of two major components: the engine and the pump head. Previously produced by Rotax and named the “Rotax 185”, the now Waterax-patented 185cc, 2-stroke, single cylinder, air-cooled engine is capable of producing 9 h.p. This same Rotax 185 engine was also adapted to power the Lazair Ultralight aircraft. The Mark 3 does not have a built in fuel tank, but instead draws from an auxiliary tank of pre-mixed 2-stroke fuel. Connected to the engine with a quick action clamp assembly is the four stage, centrifugal pump head. The stages of a centrifugal pump head refer to the number of impellers along the drive shaft, and correspond to the unit’s potential pressure output.

Much of the Mark 3’s popularity has been due to its power relative to its size. Weighing in at 55lbs, the unit measures 16¼ inches tall and 23 inches long, with a width of 12 inches. The compact nature of the Mark 3 has made it the ideal pump for helitack crews where space is limited and weight is a significant factor, or for crews in remote locations where gear needs to be hiked in or transported by ATV. The assembled unit can be worn with backpack straps for transportation on foot.

Pressure
As well as its suitability for fire suppression in remote settings afforded by its weight and dimensions, the high-pressure pump has a shut-off pressure of 295psi, and a free-flow output of 78 gallons (over 295 liters) per minute. This allows crews to maintain pressure at the nozzle over long hose lays and high elevations relative to the water source, and fight fires with increased efficiency and safety. Higher pressure at the nozzle lets crews spray burning materials from a safer distance and more effectively cut into thick brush or ground debris.

Set-Ups
Two Mark 3s can also be used in a single hose lay as a tandem setup to maintain pressure over even greater distances, where there is an initial unit pumping from the water source and then a secondary Mark 3 midway along the hose lay between the nozzle and the water source. For increased volume, two Mark 3s can pump from the same water source into separate hose lays, eventually feeding into one one hose lay which flows to the fire line.

Testing
Another reason for the Mark 3’s popularity among Wildfire agencies is its durability and endurance. In August 2015, the pump successfully completed the USDA Forest Service 100-hour endurance test. Since obtaining the rights to the engine used in the Mark 3, Waterax has invested in changes to further improve durability and weight reduction. These changes include a new nikasil-coated cylinder, a longer recoil rope, a composite cooling fan, and an impregnated crankcase.