Static pressure is defined as the pressure in the system when what condition exists?

• A. No water is flowing
• B. Water is flowing
• C. The system is pressurized with air
• D. There is a leak in the line

Answer: (A)

Static pressure is the pressure in the water system when no water is moving. It represents the pressure energy in the line at rest, such as when the discharge valve is closed and flow is interrupted. With no flow, there is no velocity head and no additional losses from friction; the pressure you measure reflects the available pressure in the system rather than anything related to moving water. When water is flowing, part of the energy becomes velocity head and overcomes friction, so the pressure reading during flow isn't static pressure. A system pressurized with air or the presence of a leak aren’t the defining conditions for static pressure, though leaks can reduce pressure.