Extinguishers handle the first 30 seconds. After that, you need fire-water systems — the engineered infrastructure that delivers water (or foam) to the seat of the fire at the pressure the code requires.
There are three core fire-water systems used in Indian buildings, and each is required by NBC 2016 Part 4 under different conditions. This guide unpacks them.
1. Wet riser system — for vertical buildings
A wet riser is a vertical pipe (rising main) permanently filled with water under pressure, with hose-reel outlets on every floor. The first responder unrolls the hose, opens the valve, and water is available within seconds.
Required for:
- All buildings above 15 m (residential, commercial, institutional, assembly)
- All buildings above 9 m in mercantile / business occupancy with high occupancy load
Core components:
- Underground or terrace static water tank (sized to occupancy class — typically 75,000 to 200,000 litres minimum)
- Main fire pump delivering code pressure (typically 3.5 kg/cm² at the topmost outlet)
- Jockey pump to maintain line pressure between draws
- Diesel back-up pump for power-failure scenarios
- Wet-riser pipe running vertically through the building (typically 150 mm dia. internal)
- Hose-reel cabinet at every floor — 30 m or 36 m hose, branchpipe, valve
Inspector checklist:
- Pressure at the topmost hydrant outlet (must be ≥ 3.5 kg/cm² when measured under flow)
- Pump auto-start test (loss of line pressure must trigger main pump start)
- Diesel pump run-up test (30 minutes under load, monthly)
- Hose reel condition (no perished rubber, no kinks)
- Static tank water level (sensor calibrated, low-level alarm working)
2. Yard hydrant system — for industrial perimeters
A yard hydrant loop is a horizontal pipe network around the perimeter of an industrial site, with hydrant outlets at intervals. Designed for fire-service deployment from the outside-in rather than occupant deployment from the inside-out.
Required for:
- All industrial / storage occupancies above 750 m² built-up area
- All petrochem / hazardous occupancies regardless of size
- All warehouses with rack storage above 4 m
- All fuel storage and dispensing facilities
Core components:
- Yard hydrant loop — typically 150 mm dia. galvanised MS pipe (Class C heavy duty)
- Single / double-headed hydrant valves at 30 m intervals (40 m on straight stretches)
- Fire service inlet for fire brigade pumper connection
- Static water tank + fire pump (often the same system as wet riser if both exist)
- Hose boxes with 63 mm-dia. hoses, branchpipes, spanner
Inspector checklist:
- Pressure at the remote-most hydrant outlet (≥ 5.25 kg/cm² static, 3.5 kg/cm² under flow)
- Hydrant valve operation (no seized stems, no leaking glands)
- Hose box completeness (hose, branchpipe, key & bar)
- Pump start-up time (within 30 seconds of pressure drop)
3. Automatic sprinkler system — for compartmentation
A sprinkler system is a network of overhead pipes fitted with thermally-activated heads. Each head opens individually when ambient temperature exceeds its rating (typically 68 °C or 93 °C), spraying water on the area below.
Required for:
- All buildings above 30 m height (mandatory)
- All assembly buildings (cinemas, banquet halls) above 500 occupants
- All shopping malls and large retail (above 500 m² per floor)
- All warehouses with rack storage (under ESFR design)
- Production zones in industrial occupancies with flammable processes
- Server rooms / data centres (often clean-agent flooding instead, but sprinklers as back-up)
Types:
| Type | Use case |
|---|---|
| Wet pipe | Default for heated indoor spaces. Pipes always filled with water. |
| Dry pipe | Unheated spaces (parking, exterior canopies). Pipes filled with compressed air. |
| Pre-action | Server rooms, archives. Water released only on detector + heat confirmation. |
| Deluge | High-hazard zones (fuel storage). All heads open simultaneously on signal. |
| ESFR (Early Suppression Fast Response) | High-pile warehouse rack storage. Larger orifice, faster response. |
Core components:
- Sprinkler pipework — typically 25 mm to 80 mm dia. depending on zone
- Sprinkler heads — pendent, upright, or sidewall depending on ceiling
- Riser nipple with control valve and flow switch per floor
- Fire pump (often shared with wet riser system)
Inspector checklist:
- Visual integrity of every head (no painting, no obstruction)
- Fusible-link / glass-bulb condition (no cracks, correct temperature rating per zone)
- Flow-switch wiring to alarm panel
- Control-valve position (must be open, lock-and-tag standard)
4. Foam / gas-flooding systems — special applications
For petrochem, paint, and solvent storage, water alone won't work. Foam-based systems overlay the burning liquid with an oxygen-barrier film. AFFF (Aqueous Film-Forming Foam) and FFFP (Film-Forming Fluoroprotein) are the two common agents.
For server rooms, switchgear rooms, and archives, gas flooding (clean agent or CO₂) is used in lieu of water. The whole room floods with agent, displacing oxygen below combustion threshold, leaving electronics undamaged.
5. Which one do you need?
Walk through this checklist:
| Question | If yes → |
|---|---|
| Building above 15 m? | Wet riser + hose reels |
| Building above 30 m? | Wet riser + sprinklers |
| Industrial site above 750 m² built-up? | Yard hydrant loop |
| Rack storage above 4 m? | ESFR sprinklers + yard hydrant |
| Petrochem / fuel storage? | Foam system + yard hydrant |
| Server room above 200 m²? | Clean-agent flooding |
| Hotel / hospital? | Wet riser + sprinklers + alarm + emergency lighting |
Most buildings need a combination. Our engineer does the assessment as part of the free site visit.
How AgniPro designs and installs these systems
We do the hydraulic calculations, select the pumps, fabricate the pipework, install with our own engineers, and commission per code. Every system is handed over with as-built drawings, pressure-test certificates, and a hydraulic calculation sheet for inspection.
Book a free site visit and we'll tell you exactly which systems your building needs.