The fire pump room is where a sprinkler system can fail at a single point. Even a correctly selected pump will not run when needed if it is installed in the wrong place, with the wrong suction arrangement, in a room that is neither heated nor ventilated. This guide is a checklist for getting the pump room right at the design stage, on the drawing board.
For inspecting an existing room on site there is a separate list: the fire pump room inspection checklist. This article is aimed at the engineer drawing the project and sets NFPA 20 and EN 12845 side by side. For selecting the pump itself, see the fire pump selection guide.
1. Location and fire separation
The pump room must not be affected by the fire it exists to fight. That is why both standards start with location.
| Topic | NFPA 20 | EN 12845 |
|---|---|---|
| Preferred location | A separate pump house or a fire-separated room within the building; the choice depends on whether the building is sprinklered and whether it is a high-rise. | Order of preference: separate building → room attached to the sprinklered building with direct outside access → compartment inside the building with direct outside access. |
| Fire resistance | Typically 1 hour in a fully sprinklered building, 2 hours in an unsprinklered one; 2 hours in high-rise buildings. A detached structure at a set distance (of the order of 15 m) may be accepted instead. | A compartment with at least 60 minutes' fire resistance; no other use permitted. |
| Protection within the room | The pump room is sprinkler protected. | The pump room is sprinkler protected. |
| Other uses | Not to be used for storage beyond fire protection equipment. | Reserved for fire protection equipment only. |
Add two practical questions at design stage: is the room exposed to flooding or surface water (at basement level, next to a sump)? Is it far enough from escape routes and high-risk areas (transformers, generator fuel stores, flammable liquid stores)? Confirm fire resistance periods and separation-distance alternatives against the current NFPA 20 edition and local regulations; in Türkiye the pump and tank provisions of the national fire regulation also apply (Turkish regulation on fire pumps and water tanks).
2. Access and maintenance space
- Direct outside access: the fire service and technicians must reach the room during a fire without passing through the building. NFPA 20 requires high-rise pump rooms to be reached from outside or via a protected exit stair; EN 12845 looks for direct outside access at every step of its order of preference.
- Door: fire resistance matching the wall, opening outwards, self-closing; no water should run in over the threshold.
- Removal route: a route and door width that allow the pump, driver and controller to be taken out later; a lifting beam or hook point for heavy items.
- Working clearances: enough room around the pump and driver for maintenance, and the working space in front of electrical panels that the electrical code requires.
- Headroom: enough height for pipework, lifting gear, the diesel exhaust and sprinklers; a cramped room makes both maintenance and ventilation harder.
3. Suction arrangement
A large share of pump failures start on the suction side: cavitation, air pockets, turbulent entry. These rules are non-negotiable in design:
- Positive suction: NFPA 20 requires water to reach a horizontal pump under positive pressure; where the water level is below the pump, a vertical turbine pump is used. EN 12845 permits suction lift under limited conditions: a foot valve, a separate priming arrangement for each pump and a limit on lift.
- Suction velocity: NFPA 20 limits suction pipe velocity to 4.57 m/s (15 ft/s) at 150% of rated flow. EN 12845 sets lower velocities at maximum demand (of the order of 1.5–1.8 m/s depending on the arrangement); confirm the value.
- Eccentric reducer: the reducer at the pump inlet must be eccentric, with the flat side on top; otherwise an air pocket forms at the crown.
- Straight pipe: on horizontal split-case pumps, at least 10 pipe diameters of straight pipe is needed between an elbow in the plane parallel to the shaft and the suction flange; otherwise flow loads one side of the impeller.
- Valves: a supervised (tamper-switched) OS&Y valve on the suction; NFPA 20 restricts butterfly valves within a set distance of the pump suction flange.
- Suction from a tank: an anti-vortex plate, adequate submergence and a strainer on open sources. For the tank side, see the fire water tank sizing guide.
- NPSH check: available NPSH must exceed the pump's required NPSH at 150% flow by a safe margin. The fire pump NPSH calculator gives a quick check.
4. Discharge side, test header and flowmeter
A pump is flow-tested on the day it is commissioned and every year of its life. If the test arrangement is not resolved in design, the test is either never done or it floods the building.
- Discharge order: pump → discharge gauge → check valve → supervised isolating valve. Get the order wrong and the system must be drained to service the check valve.
- Test header: hose valves in a number set by pump capacity, at a location where test water can be discharged safely outside. A normally closed, supervised control valve on the test line.
- Flowmeter: under NFPA 20, a meter able to measure up to 175% of the pump's rated flow, with the straight pipe lengths the manufacturer requires up- and downstream. A closed-loop meter (returning to the tank) allows testing without wasting water, but consider an open discharge option too, so annual tests see the real suction conditions.
- EN 12845: requires a flow test arrangement on the pump discharge able to verify pump performance up to full load; design the flowmeter and return line to the relevant clause together with the manufacturer's instructions.
5. Relief valves, circulation and drainage
- Circulation relief valve: prevents the water heating up while the pump runs against a closed valve. NFPA 20 requires one on each pump; on diesel pumps whose engine cooling water is taken from the pump discharge, the cooling circuit does that job.
- Pressure relief valve: needed on a diesel pump where, allowing for engine speed variation, the churn pressure plus the maximum static suction pressure exceeds the pressure rating of system components. Variable speed pumps have their own rules. Do not use a relief valve as a permanent means of reducing pressure; that is usually a sign of the wrong pump selection.
- Relief valve discharge: to a visible cone or open discharge; return to the tank is acceptable. Piping it back to the suction is restricted.
- Floor drainage: the floor should fall so that gland leakage and valve discharges run away from critical equipment to a drain of adequate capacity. In basement rooms consider a sump pump with a high-level alarm.
6. Ventilation and heating
| Topic | NFPA 20 | EN 12845 |
|---|---|---|
| Minimum room temperature | Generally 5 °C (40 °F); in diesel engine rooms, not below the engine manufacturer's recommended value. | 4 °C for electric pumps, 10 °C for diesel pumps. |
| Ventilation | Combustion and cooling air for diesel engines; room temperature kept below the upper limit for the engine and controller. | Adequate ventilation for diesel pumps to the manufacturer's instructions; the numerical airflow comes from the manufacturer. |
Ventilation in a diesel pump room does three jobs: it supplies combustion air, removes heat from radiator-cooled engines and keeps room temperature acceptable for the controller and batteries. On radiator engines the hot air should be ducted straight outside, with the fresh air louvre on the opposite side and of adequate free area. In winter those louvres can freeze the room; consider motorised dampers with thermostatic control. Heaters should be sized to rule out freezing, with insulation that holds the room temperature for a while even during a power cut.
Exhaust: the diesel exhaust should be insulated, fitted with a flexible connection for expansion and a silencer, and discharged outside away from building openings. Back pressure must stay within the engine manufacturer's limit; on long exhaust runs, check the diameter by calculation.
7. Fuel tank (diesel)
- Capacity — NFPA 20: 1 gallon per horsepower of engine output (about 5.07 L/kW), plus 5% for expansion and 5% for sump.
- Capacity — EN 12845: enough fuel for the engine to run at full load for 3 hours for LH and OH, and 6 hours for HHP and HHS.
- Location and fittings: the fuel tank may sit in the engine room; provide a bund, a level gauge, a vent pipe terminating outside, and a safe, accessible fill point. A normally open valve on the fuel line, locked or supervised; a low fuel level alarm.
- Fuel quality: water and microbial haze collect at the tank bottom; leave a drain point and a sampling facility in the design.
To compare the two standards' results, use the diesel fire pump fuel tank calculator.
8. Controllers and power supply
- Listed/approved controller: a controller listed for fire pump service, within sight of the pump and driver, protected from water spray and mounted at an adequate height above the floor.
- Reliable supply: the electric pump's supply should be taken ahead of the building's main disconnect or from an independent source; overcurrent protection is chosen to carry the pump's locked-rotor current. Cables run on a fire-protected route or are fire-resistant.
- Stopping logic: an automatically started fire pump is not stopped automatically, or only under the conditions the standard allows; verify these settings at commissioning (fire pump pressure settings at commissioning).
- Diesel controller: two separate battery sets, each with its own charger; start attempts alternate between the two.
- Signals: pump running, phase loss/reversal, controller fault and, for diesel, battery and fuel alarms should reach a constantly attended point.
- Jockey pump: keeps system pressure up against leakage; set above the main pump's start pressure. A jockey pump is not a listed fire pump and does not count as a water supply in the calculation.
For controller requirements in detail, see NFPA 20 fire pump controllers.
9. Lighting, signage and documentation
- Emergency lighting: emergency lighting in the room that works during a power cut; NFPA 20 requires that it is not connected to the diesel engine starting batteries.
- Normal lighting: enough to read gauges, the controller display and valve positions comfortably.
- Door sign: a "Fire Pump Room" sign on the outer door; a no unauthorised entry notice.
- Valve labels: each valve labelled with its function and normal position (open/closed); test valves that must stay closed marked separately.
- Schematic and records: a wall-mounted schematic, the pump curve, acceptance test results, set pressures and weekly/monthly check forms.
NFPA 20 vs EN 12845: where design differs most
| Topic | NFPA 20 | EN 12845 |
|---|---|---|
| Suction lift | Not accepted for horizontal pumps; use a vertical turbine | Accepted with conditions (foot valve, priming, lift limit) |
| Pump curve | At least 65% of rated pressure at 150% of rated flow; churn not above 140% | Selected against the demand point; curve and power conditions follow the standard's own rules |
| Diesel fuel | 5.07 L/kW + 5% + 5% | LH/OH 3 h, HHP/HHS 6 h at full load |
| Room temperature | 5 °C; manufacturer's value for diesel | Electric 4 °C, diesel 10 °C |
| Fire separation | 1 or 2 hours (by building) or distance | 60 minutes, direct outside access |
For a detailed side-by-side reading see the NFPA 20 vs EN 12845 pump comparison and, on the EN side, EN 12845 pump room requirements.
The hand-over test for the design: once the drawing is finished, ask yourself: "Could a technician, at midnight, with the building on fire and a torch in hand, get into this room from outside, start the pump by hand, read the gauges and open the test valve?" If the answer is no at any step, the room has not been designed yet.
Frequently Asked Questions
Can the pump room be in a basement?
The standards do not forbid it outright, but direct outside or protected access, fire separation, flood risk and drainage must all be resolved. EN 12845's order of preference puts a separate building and direct outside access first.
What is the minimum temperature for a diesel pump room?
At least 10 °C under EN 12845. NFPA 20 generally asks for 5 °C, but a diesel engine room must not fall below the engine manufacturer's recommended value.
How large should the diesel fuel tank be?
Under NFPA 20, about 5.07 L/kW plus 5% for expansion and 5% for sump; under EN 12845, enough for 3 hours at full load for LH/OH and 6 hours for HHP/HHS.
Is a test header needed if a flowmeter is fitted?
NFPA 20 accepts a flowmeter as a test method, but in some cases, or at the authority's preference, a hose valve test header may still be required. Either way, where test water discharges must be resolved in design.
How does this differ from the inspection checklist?
This guide is for getting the room right in the project: location, size, suction geometry, ventilation capacity. The inspection checklist is for checking a working room on site: valve positions, records, fuel and battery condition.
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Download MEP Calc on the App StoreNFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection (2022/2025) · BS EN 12845:2015+A1:2019 · NFPA 25 · Turkish Regulation on Fire Protection of Buildings. Fire resistance periods, velocity limits and distances vary between editions; the binding text is the current standard and the authority having jurisdiction.