A cutaway collection pit with an incoming drain, submersible pump and impeller, level float and switch arm, riser with check valve, and high-water overflow station are shown. Set inflow, discharge static lift, pump power, and optionally stick the float or leak the check valve, then watch the level cycle between the float setpoints.
• A real-time 3D view with numbered, clickable parts: cutaway collection pit; submersible pump and impeller; level float and switch arm; riser and check valve; incoming drain; high-water and overflow station. Scene tools include home view, focus-selected-part, auto-rotate, expand and show/hide labels, and drag-to-orbit with pinch-to-zoom. • Experiment controls: incoming water (0.2–3 L/s); discharge static lift (0–9 m); pump power available; float stuck in off position; discharge check leaks while pump is off, plus a show flow/process markers toggle, pause/resume, single-step buttons (0.1 s and 1 s), a playback-speed selector and a restart experiment action. • Live readouts: pit water level; external inflow; pump discharge; pump starts; accumulated overflow; water balance residual. A model response curve is drawn beside the 3D view and updates as you change controls. • A Curves & measurements tab with two live charts, the model equations as written in the simulator and snapshot readouts; an Experiments tab with 3 guided presets (normal automatic cycling; power failure; capacity exceeded) plus a model-verification bench, timestamped event log and copyable trial report. • A Learn & assess tab with 3 lessons (follow the system; connect the measurements; interpret the model), a 2-question knowledge check with reset, and a written model-scope statement.
The pump turns on when the pit reaches 600 mm and off at 200 mm, so each run lowers the level by a known band before stopping. The pit balance is Area dh/dt = Qin + Qback − Qpump − Qoverflow, and the simulator reports pump starts and a water-balance residual that should stay near zero.
Pump flow follows a prescribed linear curve Qpump = 4 max(0, 1 − H/10) L/s, so a higher discharge lift reduces capacity.
Power loss, a float stuck in the off position, or inflow greater than the pump can move all raise the level until water reaches the rim and overflow accumulates. A check valve that leaks while the pump is off lets discharged water run back into the pit, adding to inflow and causing extra cycles.
This is a lumped pit balance with a prescribed linear pump-versus-lift curve. It has no pipe-friction curve, motor start transient, thermal trip or electrical installation model. One animation second represents five physical seconds.
The lower float setpoint keeps the pump submerged and prevents running dry and short cycling.
It prevents water in the riser from draining back into the pit when the pump stops. If it leaks, the returned water adds to inflow.
In the model the pump curve falls linearly with head, reaching zero at 10 m, so more lift means less flow.
It is the difference between stored volume and initial volume plus inflow and backflow minus discharge and overflow, so a near-zero value confirms the bookkeeping.