In fairness, WrexTech's suggestion to measure temperature differentials on air and water sides is reasonable, though all could be gotten using a single fairly accurate digital thermometer. The $8 analog thermometers he linked are wholly unsuitable for this application, though. His advice to refer to the "owner's manual" for advice on proper system temperatures is laughably useless as well. His 3) is a bit mystifying - I guess I'm remiss in failing to furnish and install "Peach Valves" on my systems. They sound yummy, though! In addition, I'm not much into team sports, so I guess I'm also at fault for failing to comprehend the important roles of "Basketball or Football air valves" play in a modern geo system. I learn something here every day!