Transmission Loss

In this example, water is flowing at 100 liter/min through a schedule-40, 100 ft long 1"(nominal) dia pipe. The pressure required to pump this fluid is about 17.94 psi as shown below.
A 5% reduction in internal diameter (1.049" to 1,0") can cause this pressure to increase it to 22.85 psi. A 27% increase in the pressure value. This is shown below.