A cooling tower is an open basin of warm water, exposed to the air, dosed with biocide to keep it from growing things. Every part of that description is a reason to keep it out of the drinking water.
Warm standing water is where Legionella lives, which is why tower water is treated and why the treatment chemicals are aggressive. Both the biology and the chemistry put this firmly in the health hazard category.
Towers also run on circulation pumps, so backpressure is not theoretical. Health hazard with active backpressure is the clearest case in this whole list, and it goes to a reduced pressure assembly nearly every time.
Scope on this one: we test and repair. The tower may be on the roof, but the makeup assembly is almost always inside, and assemblies inside the building are not ours to replace — that is licensed plumbing work. A failure is far more often a rebuild than a replacement, and rebuilds we do on the spot. The device types, and where our work stops.
Schedule a backflow test or call 970-835-9661