Not every airfield friction tester needs the water system.
The smaller regional airports in the northern states that have colder weather may find that no rubber builds up on their surfaces over time. They may not need the water system. However, a water system is necessary for those airports that are larger or have more air traffic so rubber builds up. It is also useful for those airfields that have older degraded pavements where the timing on a resurfacing decision is necessary. The RT3® Flight with Water System is compliant with the FAA Circular 5320-12C, for the Measurement, construction, and maintenance of skid resistant airport pavement surfaces.