Our expert responds #24

QUESTION
According to the current fire regulations, it is possible to use several tanks in parallel as a water storage?

ANSWER
Great attention should be paid to the water storage formed by several tanks placed in parallel.
It is no coincidence that UNI/TR 11438 (4.2.3) states:
"The water storage must be understood as a single storage.
Splitting the water storage into several parts is to be avoided, as this could cause disruption to the entire supply system.
Situations other than the single water supply must be engineered to guarantee in any case the performance required by the system, and to ensure the continuity and reliability of the water supply for the entire expected duration, even with respect to the effects of the fire.
The availability of the water supply must be guaranteed for the entire duration of the supply, also with respect to the effects of the fire and as indicated in point 4.1.1."

This means that even at the minimum level, the tanks must be able to provide the planned flow rate.
It is therefore necessary to correctly size:

• the diameters of the outlets from the tanks
• the diameter of the intake manifolds

In the following images, we will try to provide elementary calculation methods to obtain the sizing of these elements.
These elementary calculation methods apply to:

• No more than two tanks connected in parallel to the same manifold
• Manifold length < 10 m

in the case of:

• tanks > 2
• collector lengths > 10 m

what has been described would become excessively approximate.