Here’s another Flint Hydraulics Tech Tip: Resistance to flow can be caused by an obstruction in a line such as a small orifice or a partially closed valve. In fact, everything through which oil flows resists the flow to some extent. If a faucet is wide open, it offers no resistance to the flow from the pump, and pressure will read zero PSI on a gauge. (Note: There must be pressure present or the liquid would not move, but the pressure level is too low to register on a gauge.) Need help? Call our team of troubleshooters today at 901-794-4884 or email firstname.lastname@example.org.