Our expert responds #2

3 febbraio 2020

by Idroelettrica spa

Fire-fighting water supply tanks that are not part of a single skid-mounted system.

Good evening Engineer
I would like to ask you to provide information on the fire-fighting supply tanks that are not part of a single skid-mounted system.

  • Is it possible to place a PVC tank outside?
  • Is it possible to bury a PVC tank?
  • Isn't there a risk that if the pumping unit is started up, the tank implodes on itself?

Looking forward to your kind reply, we remain at your disposal and thank you in advance.

Regarding your question, the indications that we can provide are the following:

UNI 10779: 2014 6.2.1

From which it can be deduced that metal pipes must always be used in the sections above ground.

UNI 10779: 2014 6.3

Each shut-off valve mounted on a fire-fighting network, of any type and material must follow UNI 11443:2012

- UNI 11443: 2012 7.2.1

In this article it is clearly stated that valves in thermoplastic material can only be used in systems that use tubes in thermoplastic material.

The combined provisions of the above leads to the following conclusion:

  • since only metallic materials can be used for above-ground pipes, the fittings and valves on said pipes can only be metal


outgoing fittings from the storage tanks, being external (i.e. not underground), must necessarily be metal and connect:

  • downstream of the metal pipes
  • upstream of storage tanks that may only be metal or made of REINFORCED CONCRETE.


  • All outside fire storage tanks can only be made of metal or REINFORCED CONCRETE.
  • External fire-fighting water supply storage in plastic material cannot be used
  • The fire-fighting water supply storage in plastic material can only be used for underground installation.

As for the possibility of implosion of buried tanks in plastic material, there is the possibility that this will happen.
It will therefore be necessary to take all the necessary precautions (vent pipes/air inlet with correctly sized diameter, ribbing, etc.) so that this does not happen.


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