Reuse of Fire Protection Water Storage Tanks: When designing a pumping station for a textile plant, it is common to be asked to reuse existing tanks. The answer is “yes, but”—and it depends primarily on the configuration and inlet layout.*
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The Case in Brief
You are designing a fire pump station and want to reuse two vertical iron tanks already on site, each measuring 20 m² and 3 meters high, which are not connected to each other.
The two key questions are:
- whether these tanks can be used as a water reserve;
- whether the installation should be considered above or below the door frame.
Reuse of Tanks: What Is Generally Permitted
The tanks can be reused as a water reserve. However, to ensure that the solution is technically compatible with the system, a connection to the pumps must be provided via an inlet manifold, which must be properly sized.
This point is not merely a “system-related” detail: it is one of the factors that determines the feasibility of the configuration and, above all, the ability of the water supply system to maintain the required performance.
Reuse of Fire Protection Water Reserve Tanks: Above or Below the Water Level?
The classification of the installation as “above the door” or “below the door” cannot be automatically determined solely on the basis that there are two tanks that are not connected.
The definitions that describe the above- and below-flange configurations are specified in UNI EN 12845, section 10.6.2. In practice, to answer correctly, you need to check the actual layout of the tanks, inlets, and pumps.
Based solely on the information provided in the question, it is not possible to give a definitive answer.
The Inlet Manifold: When It’s Allowed and When It’s Prohibited
There is a very clear restriction here:
- The inlet manifold leading to the pumps (if properly sized) is acceptable if the application is a suction-fed system.
- The inlet manifold is prohibited in over-the-door applications, in accordance with UNI EN 12845, 10.6.2.
This means that, even before “adapting” the solution to existing tanks, it is best to start by asking a guiding question: Does the configuration I am designing fall under the “sub-batten” category (where the collector is permitted) or the “over-batten” category (where it is prohibited)?
Two separate tanks: reliability and continuity of the reserve
When there is no single water supply, this setting must be handled with particular care. The reference cited is UNI/TR 11438 (4.1.3), which states that:
“Situations other than those involving a single water supply must be engineered to guarantee the system’s required performance in all cases and to ensure the continuity and reliability of the water supply throughout its expected service life, even in the event of a fire.”
In practical terms (without adding requirements that aren’t already there): with two separate tanks, you must design and verify the solution so that the water supply remains continuous and reliable for the expected service life, even under fire conditions.
Watch the minimum level: the design flow rate must be maintained
One specific point to note is the following: care must be taken when calculating the manifold, because the design flow rate must be guaranteed even when the tanks are at their minimum level.
This sentence alone makes it clear why the assessment cannot be limited to “can be reused / cannot be reused.” Reusability is linked to:
- inlet diagram;
- top/bottom sash configuration;
- Performance testing when the water level in the tanks is at a minimum.
What It Takes for a Truly Unambiguous (and Risk-Free) Answer
The question is correct and very practical, but the information provided is not sufficient to definitively classify the system as top-hung or bottom-hung.
To complete the verification correctly, the logical steps are:
- classify the configuration according to the definitions in UNI EN 12845 (10.6.2);
- Set up the layout, taking into account the constraint on the inlet manifold (allowed below the header, prohibited above the header);
- “engineer” the solution when there is more than one reserve, in accordance with UNI/TR 11438 (4.1.3);
- Verify that the design flow rate is maintained even when the reservoirs are at their minimum level.
Conclusion
Yes, the two existing tanks can be reused as a water reserve, but the system must be configured correctly: the inlet manifold is a critical component (allowed in under-beam systems, prohibited in over-beam systems), and with two unconnected tanks, the design must ensure performance, continuity, and reliability down to the minimum level.
