This interactive 3D model puts you inside a dedicated fire pump room and walks the full sprinkler riser assembly up through three floors — the electric fire pump and jockey pump on their housekeeping pad, the NFPA 20 fire pump controller, suction and discharge piping with their required fittings and valves, the alarm check valve and OS&Y control valve at the riser base, and the flow switches, tamper switches, and sprinkler heads that carry protection to every floor. Click any component to see what it is and what it does. It's a visual learning tool for fire protection engineers, NICET candidates, sprinkler fitters, and AHJs who need to understand how a fire pump actually keeps a sprinkler system charged.
The viewer is built around a dedicated fire pump room, not a single device in a larger building:
• Fire pump room — an electric horizontal split-case fire pump and its separate jockey pump, each with its own NFPA 20 controller, mounted on housekeeping pads. • Suction and discharge piping — the eccentric reducer on suction (flat side up, preventing an air pocket), the concentric reducer on discharge, a check valve, and a supervised OS&Y gate valve, plus suction and discharge pressure gauges. • Sprinkler riser assembly — the alarm check valve and main OS&Y control valve with its tamper switch at the riser base, then the vertical riser feeding three floors of cross mains, branch lines, and sprinkler heads. • Per-floor monitoring — a water flow switch and pressure gauge at each floor's riser takeoff. • Site connections — the backflow preventer on the incoming water service, the fire department connection (FDC) at the exterior wall, and a test header for the annual flow test.
The jockey pump quietly maintains system pressure between real demand events, cycling on and off to cover minor leakage without ever starting the much larger fire pump. When a sprinkler head actually operates, system pressure drops enough that the fire pump controller's pressure switch trips, auto-starting the main fire pump — which then runs continuously until someone manually stops it at the controller, per NFPA 20. Water travels from the pump, through the check valve and OS&Y valve, up the riser past the alarm check valve (which confirms genuine sustained flow, not just a surge, and sounds the water motor gong), and out through each floor's cross mains and branch lines to the sprinkler heads. Flow switches at each floor report exactly which level is discharging to the fire alarm system, while tamper switches on the OS&Y valves supervise that no one has closed off water supply to the system.
1. Drag to orbit the pump room and riser, scroll to zoom, and pan to move around. 2. Click any device — the fire pump, controller, valve, gauge, flow switch, or sprinkler head — to highlight it and read what it does, with its NFPA 20/13/25 reference. 3. Use the Floor buttons to isolate a single floor's riser takeoff and sprinkler heads, and the System filters to focus on just the pump, piping, monitoring, or power devices.
The jockey pump is a small pressure-maintenance pump that handles the normal, minor pressure drops from everyday system leakage or thermal expansion. Without it, the much larger and more expensive-to-cycle fire pump would be starting and stopping constantly for routine maintenance — the jockey pump exists specifically so the main fire pump only runs when there is a genuine, sustained demand.
A water flow switch detects sustained water movement in the piping — meaning a sprinkler has actually operated — and reports a true ALARM to the fire alarm control panel, after a 30–90 second retard timer filters out momentary surges. A tamper switch, by contrast, monitors an OS&Y valve's position and reports a SUPERVISORY signal (not an alarm) if the valve is moved more than two turns from fully open — flagging that someone may have shut off water supply, before flow is actually affected.
An eccentric reducer is installed flat-side-up on the suction line so the top of the pipe stays flush across the size change — this prevents an air pocket from collecting at the pipe crown, which could starve the pump impeller and cause cavitation. On the discharge side, the line runs full and pressurized, so there is no air-pocket concern, and a standard concentric (symmetric) reducer is used instead.
NFPA 25 requires a weekly no-flow churn test (the pump runs against a closed discharge valve to confirm it starts and develops rated shutoff pressure), an annual full-flow test at rated flow, 150% of rated flow, and churn conditions (typically through a test header), and quarterly functional tests of each valve tamper switch — in addition to routine visual inspection of gauges and valve positions.
An alarm check valve sits at the base of a wet-pipe sprinkler riser and, beyond simply preventing backflow like an ordinary check valve, diverts a small portion of any sustained upward water flow to a retard chamber and water motor gong or pressure switch. That mechanism is what confirms a genuine, sustained waterflow condition — a sprinkler actually operating — rather than a brief pressure surge, before an alarm is transmitted.