BAT Water System Hydraulics & Pressure Principles Flashcards

What is the significance of 'relief valve opening pressure' in an RPZ assembly test?

Answer: It verifies the relief valve opens before the first check differential drops below 2 psi

The relief valve in an RPZ must open when the differential across the first check drops to 2 psi or less, ensuring contaminated water cannot reach the supply.

What primarily causes water hammer in a piping system?

Answer: Sudden stoppage or change in flow velocity

Water hammer occurs when flowing water is suddenly stopped or redirected, creating a pressure surge or shock wave that can damage pipes and assemblies.

What is the primary hydraulic function of a check valve within a backflow prevention assembly?

Answer: Allow flow in only one direction to prevent reversal

A check valve acts as a one-way gate, opening under forward flow pressure and closing to block reverse flow that could cause backflow.

What unit is water pressure most commonly measured in during backflow field testing in the US?

Answer: Pounds per square inch (psi)

In US field testing, backflow testers use pounds per square inch (psi) as the standard unit when reading pressure gauges on test kits.

What does increasing pipe diameter do to water velocity when flow rate remains constant?

Answer: Velocity decreases

Per the continuity equation (Q = A × V), if flow rate is constant and cross-sectional area increases, velocity must decrease proportionally.

What causes 'residual pressure' to drop in a water distribution system during peak demand?

Answer: Friction losses and increased flow demand drawing down system pressure

During peak demand, high flow rates increase friction losses throughout the distribution system, resulting in lower residual pressure at service connections.