Pressure gauges are perhaps the most widely used instruments applied to the HydronicSystem. Properly used, the pressure gauge can provide valuable information relative tosystem operating and balance problems. When gauge pressures are incorrectly evaluated,however, the derived misinformation can lead to errors in terms of system operating problemdiagnosis. Balance problems can also arise because of seemingly irreconcilable mismatchesbetween summation terminal flow rates and the apparent pump delivery flow rate. This paper discusses the analysis and interpretation of pressure gauge readings.