Seawater to extinguish a fire: yes, it’s possible, but only if clear limits are observed and specific measures are incorporated during the design phase of the fire suppression system.
In this “Engineering Insights” column, we address a question that comes up frequently, especially in areas where fresh water is not readily available: Can seawater (or brackish water) be used as a fire-suppression fluid? The answer is yes, but not “directly” or indiscriminately: specific operating conditions and design considerations are required.
Table of Contents
Seawater for Firefighting: What Does UNI EN 12845 Allow?
UNI EN 12845 (section 8.1.2) permits the use of saltwater or brackish water. This clarification is important because, in certain situations, the available water may not be fresh.
That said, the approach outlined in the rules does not mean that “any water will do”: the use of saltwater or brackish water is permitted only within certain limits and under conditions that protect the system.
What are the limitations of using saltwater or brackish water?
The key issue is not just whether saltwater or brackish water can be used, but how it is used and what measures must be taken to prevent adverse effects on the system.
In particular, it is emphasized that the use of brackish water imposes operational constraints and requires that the system be managed in such a way as to prevent saltwater or brackish water from remaining in the system on a permanent basis.
Why the fire suppression system must be filled exclusively with fresh water
The rules clearly state that the fire suppression system must be filled exclusively with fresh water.
In practice, even though the water supply system may involve the use of saltwater or brackish water, the standard operating condition for the network is that it normally remains filled with fresh water. This principle guides the entire design of the water supply system and the related testing and maintenance procedures.
Design Implications: What to Consider in the Water Supply System
If the option of “using seawater to extinguish a fire” is to be made feasible, the practical implication is that dedicated components must be included as early as the water supply design phase.
In particular, solutions should be developed that allow for:
- to manage the tests without compromising the network;
- to ensure that, following any flow of brackish water, it is possible to restore the required conditions (the system filled with fresh water).
Auxiliary Fresh Water Storage System (Testing and Recirculation)
One of the first elements to be planned is an auxiliary freshwater storage system, which will allow for:
- draw in fresh water;
- Recirculate the flow rate during testing.
This point is essential because the tests must be able to be performed without causing unwanted brackish water to remain in the system, while ensuring that the system’s operation remains consistent with the requirement that the system be filled with fresh water.
Freshwater Flushing System (Pipes and Pumps)
The second key element is a freshwater washing system that allows for the complete removal of brackish water, should any have been introduced.
Removal must be possible:
- from all pipes (both Inlet and Outlet lines);
- from the pumps.
This requirement is not an “extra”: it is the measure that allows the system to be restored to proper operating conditions after any use of brackish water.
What are the risks without these measures: deposits and corrosion
Without the elements described above (auxiliary freshwater storage and freshwater flushing), the water supply and water system would be at risk of serious damage due to:
- deposits;
- corrosion.
In other words: the technical feasibility of using seawater to extinguish a fire goes beyond simply “it can be done”; it depends on the presence of systems that prevent harmful consequences for the facility.
Conclusion
Seawater for fire suppression: UNI EN 12845 (8.1.2) permits this, but the fire suppression system must be filled exclusively with fresh water, and the design must include auxiliary storage and a complete flushing system to handle testing and any passage of brackish water, thereby reducing the risk of deposits and corrosion.
