Find the cooler gpm in the Manufacturers IOM book. There will be a minimum & maximum GPM graph where you can plot your FT./head. You will need to get cooler entering water psi & cooler leaving water psi (use very accurate gauge, do not rely on the gauges installed on piping) use the pressure drop X 2.31 to find FT./head. ex. 30psig cooler inlet, 25psig cooler outlet= 5psi pressure drop X 2.31= 11.55 FT./head. Your should be able to plot this on the Graph to find out if you are moving enough water (per manuf.) through your cooler.