Submersible pumps UNI EN 12845: The standard permits their use, but not as the “first choice,” and subject to specific design and documentation requirements. In this response, I clarify what it means, in practice, to use submersible pumps as primary fire pumps and what considerations must be explicitly stated in the technical report.
Table of Contents
What Does UNI EN 12845 Say About the Use of Submersible Pumps?
UNI EN 12845 (10.6.1) permits the use of submersible pumps. This is the starting point: their use is permitted, but they are not presented as a “standard” solution to be applied without further evaluation.
In practice, when discussing UNI EN 12845 submersible pumps, it is important to consider the specifications in conjunction with the system requirements and implications: it is not enough simply to “choose a pump”; you need to design a coherent and well-founded system.
Limitations of the rules and the need for technical justification
The rules set limits on their use, stating that they should be installed only when strictly necessary and requiring a technical justification for the decision.
In operational terms, the report should explain why it was not possible to use alternative approaches, such as:
- submersible centrifugal pumps;
- VTP.
This documentation is not a mere formality: with UNI EN 12845 submersible pumps, the technical justification becomes an integral part of the design’s compliance.
Underlayment System: Why It’s “Ideal” and What It Involves
One of the most obvious characteristics of systems with submersible pumps, used as primary fire pumps, is that the hydraulic configuration is a negative-pressure system.
The original text describes it as a “clearly” underlying framework and, therefore, an ideal framework for a security system such as the one under consideration. This framing helps explain why the solution may be of interest in specific contexts, while remaining subject to limitations on its use and assessments of its overall consistency.
Installation: Horizontal Position and Cooling Coils
To minimize volume loss inside the tank, the pumps must be installed horizontally.
In addition, to prevent the electric motor from overheating, the machines must be housed inside cooling chambers designed to allow water to enter only from the rear. As the water flows past the motor, it keeps it at the correct temperature.
This means that, when designing systems with submersible pumps compliant with UNI EN 12845, the focus is not solely on “hydraulics”: the physical configuration of the installation and cooling also become explicit elements of the system.
Pressurized Piping and Flexible Placement of the Water Reserve
The pipes connecting the pumps to the room are under pressure. This makes it possible to locate the fire protection water supply in a different place than the one chosen for the equipment room.
The text highlights the usefulness of this feature when architectural or landscape constraints must be observed: the water reservoir can be buried underground, and the facility can be located even tens of meters away from the reservoir.
In terms of calculating head, to determine the design head for pumps, simply add the following:
- the network’s design priority;
- the pressure drops between the pumps and the room.
Pump Room: Requirements and References to UNI/TR 11438 and UNI 11292
With regard to the characteristics of the premises, the text also refers to UNI/TR 11438:2016, section 7.1, which explicitly states that the premises—even when submersible pumps are used—must comply with the requirements of:
- UNI EN 12845:2020
- UNI 11292:2019
The key point is the warning: apart from the PUMP–SET requirement (which does not apply in this case), all other requirements set forth in the cited rules, including the minimum height, must be met.
Therefore, even though UNI EN 12845 submersible pumps change certain installation requirements, they do not “simplify” the requirements for the pump room: the pump room remains a regulated element that must be inspected.
Water supply: single-line only (never more than one) with submersible pumps
When using submersible pumps as primary fire pumps, only SINGLE-SOURCE WATER SUPPLIES may be established; SUPERIOR-TYPE SUPPLIES are never permitted.
The reason given is straightforward: it is not possible to connect a diesel engine directly to the pump housing, since the pump is mounted in the water.
This is an important design constraint: if the system requirements call for a higher-capacity water supply, the use of submersible pumps compliant with UNI EN 12845 is not feasible under the conditions described.
Electrical Reliability and Generators: Benefits and Responsibilities
To achieve a higher level of reliability (not from a regulatory standpoint, but from a functional one), it has become common practice to use a generator set as a backup power source.
This is also to comply with the requirements of the Decree on Electrical Installations (Decree of the Ministry of Infrastructure, December 20, 2012), which stipulates that, in the absence of certification by the electricity grid operator, the professional must independently certify the required continuity and reliability, thereby assuming significant civil and criminal liability.
The generator set minimizes the risk of the fire-fighting water supply being shut down due to a power outage. However, even in presence of a generator set, it is still necessary to configure the pump control panels in accordance with the required specifications (as referenced in the text and highlighted in the figure).
Operational Conclusions
UNI EN 12845 submersible pumps are permitted, but they must be selected and described in detail: technical justification, schematic diagram, installation and cooling methods, room requirements, and implications for the type of water supply. In addition, the continuity of the power supply and the connections to the control panels remain issues that must be handled with care.
