Head loss is a disadvantaging factor in plumbing system. Because it lowers the pressure in fluid flow. Head loss is devided into major head loss and minor head loss. Major head loss occurs on straight pipe due to the friction with pipe wall and minor head loss occurs due to the influence of fitting, valve, etc. There are three fluid flow regimes, those are laminar, transition, and turbulence flow regimes. The differences among those three regimes are caused by fluid density, pipe diameter, flow speed, and fluid viscosity. This research aims to find out the effect of fluid flow debit variation on the condition of transition flow regime towards major head loss and friction coefficient on PVC pipe 12 ”. The method of data collection used was experimental by varying the fluid flow debit which entered the measurement pipe. The fluid flow debit is adjusted on transition flow regime which has Reynolds number of 2300<Re<4000 and measured with a rotameter by arranging 2 gate valves which were installed on the pipe chain. The fluid used in this study was water. The calibrated differential pressure meter was installed on the pre-determined spots to collect pressure margin data. Based on the pressure margin on the experiment, major head loss was obtained to calculate friction coefficient that occured. The result shows that fluid flow debit and Reynolds number of 2300<Re<4000 on the measurement pipe affects the size of major head loss and friction coefficient. The higher the fluid flow debit and Reynolds number, the more major head loss increases and friction coefficient decreases. The result also shows an increase of major head loss and a decrease of friction coefficient on some fluid flow debit variations and Reynolds number. By increasing the fluid flow debit and Reynolds number on the fluid flow, it is concluded that the average major head loss increase is 4,31x10−3m and the average friction coefficient decrease is 5,50x10−2.