Orifice plate meter has advantages over other flowmeters that are relatively cheap component prices, simple construction, and can be used for large pipe size. Orifice plate meter is a flowmeter that uses the principle of differential pressure. The selection of PVC pipe with 1 and ½ inch size in this research because it was easy to get in the market, and the use of U-tube Manometer aimed to get pressure data which more precision. The purpose of this research was to know the capacity or the flow rate of the orifice with beta ratio β = 0,19 in 1 and ½ inch pipe, also comparing it with actual flowrate. The use of similar beta ratio was expected that orifice plate meter can be used to predict the flowrate at 1 inch PVC pipe. The pressure gauge used in this research was U-tube Manometer which has a high value precision. The orifice plate used was 3 mm acrylic. The varied parameter was the actual flowrate shown on rotameter. The differential pressure was measured every 1 – 10,5 LPM with an increase of 0,5 LPM. Data of differential pressure who obtained then calculated to get the coefficient of discharge value and flowrate of the orifice. The orifice flowrate of the calculation result has a value that almost equal with actual flowrate shown on rotameter. The highest difference of flowrate on 1 inch pipe occurred in the 3rd and 11th experiments at 4 %, while the highest difference of flowrate on ½ inch pipe occurred in the first and second experiments at 3 %. The Coefficient of discharge value on both pipe that has been calculated then processed to compare the precentage of deviation value that occurred. The highest deviation occurred at Reynolds numbers 4200 of 12 %. Assuming ΔCd ≤ 15%, therefore Cd 1" was considered to be equal to Cd ½", then the orifice plate with the same beta ratio can be used to predict the flowrate at 1 inch PVC pipe.