To make sure that the water meter is precise, some calibration is needed with acoordance to some technical condition. The installation process of the water meter has to follow the step that has been prepared beforehand. If it doesn’t follow the step, some error may occur from the water meter reading. The position of water meter could also affect the reading of the water meter. The data gained from this research are both in the from of error value and the inaccuracy of the water meter in both position. The result of this research has shown that the water in vertical position has less error than the water neter in horizontal position. Higher error value from horizontal water meter caused by friction from the water meter’s rotor which turning the register. This friction leads to a higher inaccuracy in water meter’s reading. Then a program is made to find out the error in the water meter that can find out the validity or cancel the error in the water meter testing directly with the graph output.