Non-return Valves

Non-return Valves

We could blame it on climate change or on the “irresponsibility” of men, but it is a fact that more and more often, the rains that hit our country cause considerable problems of flooding in buildings. The sudden and massive fall of several millimeters of water does not find a correct outlet and this generates water returns inside the buildings. Very often, despite the knowledge of the reasons that cause these problems, it is not possible to radically intervene on the sewer network and, therefore, it becomes necessary to adopt a solution directly on the building to be protected from flooding risks. This solution is called Non-return valve.

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What is it and what are the causes of reflux

Knowing the principle of “communicating vessels”, according to which water tends to maintain the same level in all branches of a hydraulic circuit, when we talk about reflux, we define the maximum water level of a hydraulic circuit beyond which the leaking from the circuit itself. For this reason, if the sanitary utilities are below the ebb level (basically basements, cellars, garages, but also living quarters that are in any case below the level of the road level), flooding can occur during overload of the sewer network. The reasons for the reflux effect may be the following:

  • An incorrectly designed drainage system
  • High hydraulic flows caused by short but very intense rainfall
  • Increase in the volumes of rain channeled by collectors in relation to the building increase and urbanization
  • Water overload due to contemporaneity peaks in areas with high urban density
  • Malfunctions and occlusions downstream of the drainage system

Backflow protection applies both where a separation between white and black water has been adopted, and where there is mixed water.

The non-return valve as a protection and safety solution for homes

The non-return valve is housed in a suitable accessible and inspectable well. Its role is to create an effective barrier to any return of water flow coming from the sewerage system during any possible overload event. The non-return valve is equipped with a stainless steel plate that pivots in the direction of the water flow from the building to the sewer system. In the case of an ebb, the plate closes mechanically with the thrust of the water. The plate, acting on a special lever, can be permanently hermetically locked. The non-return valve is foreseen during the design and sizing of the building drainage system according to UNI 12056-3. Furthermore, its use is absolutely recommended in existing buildings, where it is possible to intervene on the connection piping to the sewer network and there is the physical space to create a pit that houses the valve. The non-return valve must be approved in accordance with the European standard EN 13564-1: 2003 which guarantees its requirements, such as: effective flow, non-deformability, resistance, hydraulic seal, compliance of connection, correct opening / closing operation.


Many of the respiratory problems are related to the lack of air exchange inside homes. Take a closer look at the causes that determine the unhealthiness of the house. Through proper design rules and regulations it will be possible to achieve the long-awaited well-being.

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