What is 'hydraulic jump' in the context of a horizontal drainage pipe?

Question: What is 'hydraulic jump' in the context of a horizontal drainage pipe?

Answer options:

• The splashing that occurs when waste drops down a vertical stack. ✅ An increase in the depth of flow that occurs when the pipe slope decreases suddenly or runs into an obstruction.
• A pressure surge caused by the rapid closing of a valve.
• The minimum velocity required to keep solids suspended in the flow.

Correct answer: An increase in the depth of flow that occurs when the pipe slope decreases suddenly or runs into an obstruction.

Explanation: Hydraulic jump is a phenomenon where rapidly flowing liquid (supercritical flow) in a partially full pipe suddenly transitions to a slower, deeper flow (subcritical flow), often at the base of a stack or a change to a lesser grade. This jump can cause pressure fluctuations and must be accommodated in drainage design to prevent backups.