Among the many flow rate measurement methods used in the fluid mechanics of a closed pipeline, the type of gauge using a pressure difference method is the frequently used orifice plate meter. PVC pipes are generally used as water channels in a housing project, building, etc. This PVC pipe is hard, light and strong. Because the installation is easy, it is ideal if used for the installation of household piping. Even the use of PVC pipe can work better than using iron pipe that needs to be soldered, also resistant to almost any alkaline or toxic substances and easily installed. The selection of ½ inch and ½ inch PVC pipe in this study considers several things. First, the size of ½ inch and ½ inch PVC pipe is very easy to obtain. Second, the construction of the research tool is not too large. Because according to the calculation of fully developed, the larger diameter PVC pipe used then require a longer pipe to determine fully developed. The purpose of this research is to know the effect of using orif z this study is expected to help predict the water discharge at other pipe size. This study was conducted on ½ inch and ½ inch PVC pipe using the ratio D = 0.19 using water as a fluid. Determine fully developed to place a digital pressure manometer as a pressure gauge. Parameters varied ie the actual discharge shown on the rotameter, pressure differential measurement is done from 1 to 8 LPM with increase of 0.5 LPM. After the pressure difference values are obtained, then the calculation can be done to determine the value of orifice discharge and coefficient of discharge on PVC pipe with ½ inch and ¾ inch size. T x pipe is directly proportional to the value of ̇ . There is a value deviation on ̇ with the result of calculation ̇ . In ½ inch PVC pipes, the largest deviation occurs at the value of ̇ 5.5 LPM with 24%. In ¾ inch PVC pipe, the largest deviation occurs at the value of ̇ 8 LPM with 33%. By interpolating the value of Cd ¾ inch with b b 26 88% happened at Reynolds number 1360 and the smallest deviation happened at R y 386 25% T ≤ 5% 2 Reynolds number 2200 to 5360. Based on this assumption this hypothesis can be used to estimate water discharge for different pipe size with the same ratio in this ( " " " ) q 4