Effluent reaches the leaching bed by gravity flow due to which mechanism?

Effluent reaches the leaching bed by gravity flow due to which mechanism?

• A. Pumping pressure
• B. Volume of sewage entering the tank
• C. Capillary action
• D. Venturi suction

Answer: (B)

Gravity flow in a septic system is driven by hydrostatic pressure from the liquid column. As more wastewater enters the tank, the liquid level rises, increasing the hydrostatic head at the outlet. That head pushes effluent through the outlet pipe and into the leaching bed, all under the pull of gravity rather than a pump. So the amount of sewage entering the tank directly controls the height of the liquid column, which in turn determines the pressure that moves the effluent downward to the leach field. The other ideas don’t fit the real mechanism: there’s no pump providing pushing pressure in a gravity-fed system; capillary action is a surface, small-scale effect and isn’t what moves effluent through the soil absorption system; and Venturi suction involves creating suction with constricted flow, which also isn’t how gravity-fed septic systems operate.

Gravity flow in a septic system is driven by hydrostatic pressure from the liquid column. As more wastewater enters the tank, the liquid level rises, increasing the hydrostatic head at the outlet. That head pushes effluent through the outlet pipe and into the leaching bed, all under the pull of gravity rather than a pump. So the amount of sewage entering the tank directly controls the height of the liquid column, which in turn determines the pressure that moves the effluent downward to the leach field.

The other ideas don’t fit the real mechanism: there’s no pump providing pushing pressure in a gravity-fed system; capillary action is a surface, small-scale effect and isn’t what moves effluent through the soil absorption system; and Venturi suction involves creating suction with constricted flow, which also isn’t how gravity-fed septic systems operate.