The sprinkler pump is the only active component of the system; everything else is passive. TS EN 12845+A2:2026 collects the pumps under Clause 10 and, with amendment A2, requires the pump sets to comply with EN 17451 (Clause 10.1, EN p.57). This article deals with the provisions of Clause 10 that bind the design, and in particular with the multiple pump arrangement. Source: TS EN 12845+A2:2026, Clause 10, EN p.57-66 (TSE p.60-69).
1. Multiple pump arrangement (Clause 10.2)
Clause 10.2 (EN p.57) is four sentences long and contains four independent rules:
- Compatible curves: the pump sets shall have compatible characteristic curves and shall be able to operate in parallel at all possible flows.
- Two pump case: where two pumps are installed, each shall be capable of providing the specified flows and pressures independently. That is 2 x 100 % redundancy.
- Three pump case: where three pumps are installed, each pump shall be capable of providing at least 50 % of the specified flow at the specified pressure.
- Diversity of drive: where more than one pump is installed on a superior or duplicate water supply, not more than one of them may be driven by an electric motor.
The fourth rule is the pump side counterpart of the duplicate supply logic: it prevents a power failure from disabling both pumps at once. Clause 9.6.3 (EN p.56) defines a duplicate water supply as "two single water supplies each independent of the other" and requires each of them to comply with the pressure and flow characteristics of Clause 7.
Field note: in a three pump arrangement each pump delivering 50 % means that two pumps must run simultaneously to obtain the full flow. This makes compatibility in parallel operation (rule 1) more critical in a three pump arrangement than in a two pump one.
2. The pump room (Clause 10.3)
| Subject | Provision | Source |
|---|---|---|
| Fire resistance | At least 60 minutes; not used for any purpose other than fire protection | Clause 10.3.1, EN p.57 |
| Location (in order of preference) | a) a separate building; b) a building adjoining the sprinkler protected building with direct access from outside; c) a compartment inside the sprinkler protected building with direct access from outside | Clause 10.3.1, EN p.57 |
| Sprinkler protection | Pump set compartments are protected by sprinklers | Clause 10.3.2, EN p.58 |
| Temperature | ≥ 4 °C for electric pump sets; ≥ 10 °C for diesel pump sets | Clause 10.3.3, EN p.58 |
| Ventilation | Adequate ventilation of diesel pump set compartments in accordance with the supplier's recommendations | Clause 10.3.4, EN p.58 |
Clause 10.3.2 gives a detailed alternative: where the pump compartment is separate, it may not be practical to provide the sprinkler protection from the control valve sets within the premises. In that case the protection may be provided from the nearest accessible point downstream of the pump outlet check valve, through a subsidiary stop valve secured in the open position and a water flow detector conforming to EN 12259-5; the detector gives visual and audible indication that the sprinklers have operated. The alarm equipment is installed either at the control valves or at a location with responsible personnel in attendance, such as a gatehouse. To allow the practical testing of the alarm, a drain and test valve of 15 mm nominal size is fitted downstream of the flow alarm.
3. Water temperature limit (Clause 10.4)
Clause 10.4 (EN p.58) is a separate heading and gives two values:
- The water supply temperature shall not exceed 40 °C.
- Where submersible pump sets are used, the water temperature shall not exceed 25 °C; this limit does not apply where the motor is proven suitable for temperatures up to 40 °C.
4. Valves and accessories (Clause 10.5)
Clause 10.5 (EN p.58) regulates the fittings around the pump:
- Unless the maximum water level is below the pump, a stop valve is fitted in the pump suction pipe.
- A check valve and a stop valve are fitted in the delivery pipe of each pump.
- For booster pumps, a bypass with a check valve and two stop valves, all of the same diameter as the trunk main, is installed around the pumps.
- A taper pipe fitted at the pump outlet expands at an angle not exceeding 20° in the direction of flow; the valves on the delivery side are fitted after the taper pipe.
- Provision is made for venting all cavities of the pump casing (not required where the pump is self venting by virtue of the branch arrangement).
- A continuous flow of water is provided to prevent overheating while the pump runs against a closed valve. This flow is taken into account in the system hydraulic calculation and in the pump selection. The outlet shall be clearly visible and, where there is more than one pump, the outlets shall be separate.
- Diesel engine cooling circuits generally use the same water; where additional water is used, this too is taken into account.
- The tapping points on the pump for inlet and outlet pressure gauges shall be readily accessible.
5. Suction conditions (Clause 10.6)
Clause 10.6.1 (EN p.59) prefers a positive suction head:
- Wherever possible, horizontal centrifugal pump sets are installed with a positive suction head. This has two criteria: at least two thirds of the effective capacity of the suction tank shall be above the pump centre line; and the pump centre line shall not be more than 2 m above the low water level of the suction tank (level X in Clause 9.3.5).
- Where this is not possible, the pump may be installed with a suction lift or vertical turbine pumps may be used. The standard recommends that suction lift and submersible arrangements be avoided and used only where it is impractical to arrange a positive suction head.
Suction pipe diameters:
| Suction condition | Minimum diameter | Maximum velocity (at maximum demand flow) | Additional constraint | Source |
|---|---|---|---|---|
| Positive head | 65 mm | 1.8 m/s | With more than one pump set the suction pipes may be interconnected only where stop valves are provided such that each pump set continues to operate when the other is taken out for maintenance | Clause 10.6.2.2, EN p.59-60 |
| Suction lift | 80 mm | 1.5 m/s | With more than one pump set the suction pipes shall not be interconnected; the height from the low water level to the pump centre line shall not exceed 3.2 m; a foot valve is fitted at the lowest point of the suction pipe | Clause 10.6.2.3, EN p.60 |
The NPSH requirement was clarified by A2 (Clause 10.6.2.1, EN p.59): the suction pipe, including valves and fittings, is designed so that at the maximum pump set flow shown in Table 14 and in accordance with EN 17451, the available NPSH (calculated at the maximum anticipated water temperature) exceeds the required NPSH by at least 1 m. In addition, the pump suction is connected to a straight or tapered pipe at least two diameters long; the top surface of the taper pipe shall be horizontal and the total included angle shall not exceed 20°. The suction pipe is laid horizontally or rising continuously and slightly towards the pump, so that air locking is prevented.
Table 14: Pump pressure and flow rating
| Pipework | Hazard class | Pump nominal flow | Pump inlet condition |
|---|---|---|---|
| Pre-calculated | LH/OH | The pressure and flow requirements of Table 6 | For tanks, with the water supply at low water level (X in Figure 4) |
| Pre-calculated | HH | The pressure and 1.4 times the flow required from Table 7 | For booster pumps, with the minimum town main pressure |
| Fully calculated | All | The maximum pressure and flow required for the most favourable area | - |
Source: Table 14, Clause 10.6.2.1, EN p.59 (TSE p.62).
Here the factor of 1.4 applies to the nominal flow of the pump in HH pre-calculated systems; the same 1.4 factor is also used in Clause 8.5.1 d) (EN p.44) for the capacity of the flow meter. TS EN 12845+A2 contains no pump curve acceptance criterion of the form "at least 70 % (or 65 %) of the pressure at 140 % flow".
Priming arrangement
Under suction lift conditions a separate automatic priming arrangement is fitted to each pump set (Clause 10.6.2.4, EN p.60). The arrangement consists of a tank at a level above the pump and a pipe connection sloping from the tank to the delivery side of the pump; a check valve is fitted in this connection. The tank keeps the pump and the suction pipework within the pump set continuously full of water, even if the foot valve leaks. Where the water level in the tank falls to 2/3 of the normal level, the pump shall start; alternatively, an alarm is transmitted to a continuously manned location that will ensure immediate attention.
| Hazard class | Minimum tank capacity | Minimum priming pipe diameter |
|---|---|---|
| LH | 100 litres | 25 mm |
| OH, HHP and HHS | 500 litres | 50 mm |
Source: Table 15, Clause 10.6.2.4, EN p.62 (TSE p.65).
Pressure maintenance (jockey) pump
Clause 10.6.2.5 (EN p.60): a pressure maintenance pump may be installed to prevent one of the main pump sets from starting unnecessarily, or to maintain the system pressure above the control valve sets on supplies such as a town main with fluctuating pressure. The NOTE states that some water authorities may not permit a pressure maintenance pump on systems connected to a town main.
The binding constraint is this: the pressure maintenance pump is sized and arranged so that it cannot provide sufficient flow and pressure for a single open sprinkler and thereby prevent the main pump set(s) from starting. For pressure maintenance pumps installed with a negative suction, the suction pipe and fittings shall be independent of those of the main pump.
6. Performance characteristics (Clause 10.7)
Table 16: Minimum pump characteristics for pre-calculated LH and OH systems
Where the pump sets draw water from a storage tank, the pump set selected shall comply with the characteristics of Table 16 (Clause 10.7.1, EN p.62). The table gives three points for each class: the nominal values and two characteristic points.
| Hazard class | h (height of sprinklers above the control valve set) | Nominal bar / l/min | Characteristic-1 bar / l/min | Characteristic-2 bar / l/min |
|---|---|---|---|---|
| LH (wet or pre-action) | h ≤ 15 m | 1.5 / 300 | 3.7 / 225 | - |
| LH | 15 < h ≤ 30 m | 1.8 / 340 | 5.2 / 225 | - |
| LH | 30 < h ≤ 45 m | 2.3 / 375 | 6.7 / 225 | - |
| OH1 wet or pre-action | h ≤ 15 m | 1.2 / 900 | 2.2 / 540 | 2.5 / 375 |
| OH1 wet or pre-action | 15 < h ≤ 30 m | 1.9 / 1 150 | 3.7 / 540 | 4.0 / 375 |
| OH1 wet or pre-action | 30 < h ≤ 45 m | 2.7 / 1 360 | 5.2 / 540 | 5.5 / 375 |
| OH1 dry/alternate; OH2 wet or pre-action | h ≤ 15 m | 1.4 / 1 750 | 2.5 / 1 000 | 2.9 / 725 |
| OH1 dry/alternate; OH2 wet or pre-action | 15 < h ≤ 30 m | 2.0 / 2 050 | 4.0 / 1 000 | 4.4 / 725 |
| OH1 dry/alternate; OH2 wet or pre-action | 30 < h ≤ 45 m | 2.6 / 2 350 | 5.5 / 1 000 | 5.9 / 725 |
| OH2 dry/alternate; OH3 wet or pre-action | h ≤ 15 m | 1.4 / 2 250 | 2.9 / 1 350 | 3.2 / 1 100 |
| OH2 dry/alternate; OH3 wet or pre-action | 15 < h ≤ 30 m | 2.0 / 2 700 | 4.4 / 1 350 | 4.7 / 1 100 |
| OH2 dry/alternate; OH3 wet or pre-action | 30 < h ≤ 45 m | 2.5 / 3 100 | 5.9 / 1 350 | 6.2 / 1 100 |
| OH3 dry/alternate; OH4 wet or pre-action | h ≤ 15 m | 1.9 / 2 650 | 3.0 / 2 100 | 3.5 / 1 800 |
| OH3 dry/alternate; OH4 wet or pre-action | 15 < h ≤ 30 m | 2.4 / 3 050 | 4.5 / 2 100 | 5.0 / 1 800 |
| OH3 dry/alternate; OH4 wet or pre-action | 30 < h ≤ 45 m | 3.0 / 3 350 | 6.0 / 2 100 | 6.5 / 1 800 |
Source: Table 16, Clause 10.7.1, EN p.62-63 (TSE p.65-66). NOTE 1: the pressures shown are those measured at the control valve set(s). NOTE 2: for buildings exceeding the heights shown, it shall be demonstrated that the pump characteristic is adequate to provide the flows and pressures specified in Clause 7.3.1.
HHP and HHS, fully calculated systems, boosted town mains
- Clause 10.7.2 (EN p.63): for HHP and HHS pre-calculated systems without in-rack sprinklers, the nominal flow and pressure of the pump set shall comply with Clause 7.3.2. That is the whole clause; it has no subclauses.
- Clause 10.7.3 (EN p.63): for fully calculated systems the pump set is selected to meet the pressure and flow demand of the sprinkler system (see Figure 7).
- Clause 10.7.4 (EN p.63): for boosted town mains, a test is carried out to demonstrate that the unboosted supply provides the maximum demand flow plus 20 % at a pressure of at least 0.5 bar measured at the pump inlet. This test is carried out at the time of maximum demand on the main.
Pressure switches and start/stop logic
- Clause 10.7.5.1 (EN p.63): two pressure switches are provided to start each pump set. The pipe to the switches shall be at least 15 mm. The switches are connected so that either switch will start the pump set.
- Clause 10.7.5.2 (EN p.63): the first pump set shall start automatically before the pressure in the trunk main falls below 0.8p, where p is the pressure under closed valve conditions. Where two pump sets are installed, the second pump set shall start before the pressure falls below 0.6p. Once a pump has started it shall continue to run until stopped manually.
- Clause 10.7.5.3 (EN p.64): means are provided to test the starting of the pump set by each pressure switch. Where an isolating valve is placed in the connection between the trunk main and the pressure switch, a check valve is fitted in parallel with the isolating valve so that a fall in pressure in the trunk main is transmitted to the switch even when the isolating valve is closed.
There is no automatic stop. This is one of the most categorical provisions of EN 12845 and it translates directly into the automation design.
7. Provisions specific to the type of drive
Electric pump sets (Clause 10.8, EN p.64-65):
- The electrical supply system shall be available at all times (10.8.1.1).
- The pump set shall run at its rated capacity within 15 seconds of starting (10.8.1.3).
- The supply shall be dedicated to the sprinkler system and separate from all other connections (10.8.2).
- Power cables shall be flame retardant and shall exhibit type B or C burning behaviour in accordance with EN 60332; the conductor cross section shall be at least 2.5 mm² Cu (10.8.2).
- Where the sprinkler systems are fed from two electrical sources, the cables to the pump set shall be laid at least 3 m apart from each other (10.8.2).
- Every switch in the dedicated supply line to the sprinkler pump set is labelled: SPRINKLER PUMP MOTOR SUPPLY - NOT TO BE SWITCHED OFF IN THE EVENT OF FIRE. The lettering shall be at least 10 mm high and white on a red background; the switch is locked against interference (10.8.3.2).
- The cable cross section calculation is based on 150 % of the greatest possible full load current of the pump set (10.8.4).
- Conditions to be monitored: availability of power to the motor (on all three phases for AC), pump on demand, pump running, failure to start (10.8.5.1).
Diesel pump sets (Clause 10.9, EN p.65-66): with A2 this clause has largely been transferred to EN 17451. Diesel driven pump sets and their auxiliary equipment shall conform to EN 17451; there shall at all times be sufficient clean air in the pump room to run the diesel pump set within the limits specified by the manufacturer and in accordance with EN 17451 (10.9.1). Clause 10.9.2 requires four conditions to be indicated by warning lamps both locally and at a location with responsible personnel in attendance: pump running, failure to start, common faults, automatic mode off. Site commissioning tests are carried out in accordance with EN 17451 (10.9.3).
8. The pump in the maintenance programme
| Interval | Activity | Source |
|---|---|---|
| Weekly | Automatic pump set starting test: fuel and oil levels for diesel; reduction of the water pressure at the starting device; checking and recording the starting pressure when the pump starts; oil pressure for diesel and the flow of cooling water in open circuit cooling | Clause 20.2.2.4, EN p.119 |
| Weekly | Diesel engine restart test: the engine is run for 20 min (or the period recommended by the supplier), stopped and immediately restarted using the manual start button | Clause 20.2.2.5, EN p.119 |
| Quarterly | Each water supply is tested with each control valve set in the system; where fitted, the pump(s) shall start automatically and the supply pressure at the relevant flow shall not be less than the appropriate value according to Clause 10 | Clause 20.3.2.5, EN p.121 |
| Annually | Each water supply pump set is tested at full load condition (with the test line connection made downstream of the pump set outlet check valve) and shall give the pressure and flow values stated on the nameplate | Clause 20.3.4.2.1, EN p.122 |
| Annually | The diesel failed-to-start alarm is tested for compliance with Clause 10.9.7.2; immediately after the test the engine is started using the manual starting system | Clause 20.3.4.3, EN p.122 |
| Annually | The pump set suction strainers and the settling chamber and screens are inspected and cleaned where necessary | Clause 20.3.4.5, EN p.122 |
Frequently Asked Questions
What capacity must each pump have when two or three pumps are installed under EN 12845?
TS EN 12845+A2:2026 Clause 10.2 (EN p.57): where two pumps are installed, each shall be capable of providing the specified flows and pressures independently. Where three pumps are installed, each pump shall be capable of providing at least 50 % of the specified flow at the specified pressure. In addition, the characteristic curves of the pump sets shall be compatible and they shall be able to operate in parallel at all possible flows.
How many pumps may be electrically driven?
Clause 10.2 (EN p.57): where more than one pump is installed on a superior or duplicate water supply, not more than one of them may be driven by an electric motor.
Can a sprinkler pump stop automatically?
No. Clause 10.7.5.2 (EN p.63) is explicit: 'Once a pump has started it shall continue to run until stopped manually.' The same clause also gives the starting thresholds: the first pump set shall start automatically before the pressure in the trunk main falls below 0.8p, where p is the closed valve pressure; where two pump sets are installed, the second shall start before the pressure falls below 0.6p.
What requirements apply to the pump room?
Clause 10.3.1 (EN p.57): pump sets are housed in a compartment with a fire resistance of at least 60 minutes that is not used for any purpose other than fire protection. The order of preference is: a separate building; a building adjoining the sprinkler protected building with direct access from outside; a compartment inside the sprinkler protected building with direct access from outside. Clause 10.3.2 requires the compartment to be protected by sprinklers, and Clause 10.3.3 requires a minimum of 4 °C for electric pump sets and 10 °C for diesel pump sets.
What is the temperature limit for the water entering the pump?
Clause 10.4 (EN p.58): the water supply temperature shall not exceed 40 °C. Where submersible pump sets are used, the water temperature shall not exceed 25 °C unless the motor is proven suitable for temperatures up to 40 °C.
How is a jockey (pressure maintenance) pump sized?
Clause 10.6.2.5 (EN p.60): the pressure maintenance pump shall be sized and arranged so that it cannot provide sufficient flow and pressure for a single open sprinkler and thereby prevent the main pump sets from starting. Where installed with a negative suction, the suction pipe and fittings shall be independent of those of the main pump.
References
- TS EN 12845+A2:2026 Clause 9.6.3 Duplicate water supplies (EN p.56 / TSE p.59)
- TS EN 12845+A2:2026 Clause 10.1 General - EN 17451 (EN p.57 / TSE p.60)
- TS EN 12845+A2:2026 Clause 10.2 Multiple pump set arrangement (EN p.57 / TSE p.60)
- TS EN 12845+A2:2026 Clause 10.3.1-10.3.4 Pump set compartments (EN p.57-58 / TSE p.60-61)
- TS EN 12845+A2:2026 Clause 10.4 Maximum temperature of the water supply (EN p.58 / TSE p.61)
- TS EN 12845+A2:2026 Clause 10.5 Valves and accessories (EN p.58 / TSE p.61)
- TS EN 12845+A2:2026 Clause 10.6.1-10.6.2.5, Table 14, Table 15 (EN p.59-62 / TSE p.62-65)
- TS EN 12845+A2:2026 Clause 10.7.1, Table 16 (EN p.62-63 / TSE p.65-66)
- TS EN 12845+A2:2026 Clause 10.7.2-10.7.5.3 (EN p.63-64 / TSE p.66-67)
- TS EN 12845+A2:2026 Clause 10.8.1-10.8.5 Electric pump sets (EN p.64-65 / TSE p.67-68)
- TS EN 12845+A2:2026 Clause 10.9.1-10.9.3 Diesel pump sets (EN p.65-66 / TSE p.68-69)
- TS EN 12845+A2:2026 Clause 20.2.2.4-20.2.2.5 Weekly routine (EN p.119 / TSE p.122)
- TS EN 12845+A2:2026 Clause 20.3.2.5 Quarterly routine - water supplies (EN p.121 / TSE p.124)
- TS EN 12845+A2:2026 Clause 20.3.4.2.1, 20.3.4.3, 20.3.4.5 Annual routine (EN p.122 / TSE p.125)
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Download MEP Calc on the App StoreTS EN 12845+A2:2026 (EN 12845:2015+A2:2026) Fixed firefighting systems — Automatic sprinkler systems — Design, installation and maintenance; TS EN 12845-2:2025 (EN 12845-2:2024) ESFR and CMSA sprinkler systems. Every figure in this article is taken from the published standard text; clause, table and page references are listed under References. General information only, not a substitute for the standard or for a design review.