Water is precious and it belongs to us all. Notwithstanding the law provisions, the protection of water distribution systems is key in modern installations.
That is why they require devices that prevent the backflow of potentially polluted water.
Hydraulic backflow preventers protect the public grids from possible backflows in ducts or devices that change or may change in any way the original drinking qualities, although supplied or reintegrated with aqueduct water (technical systems and civil or industrial devices).
Backflows may depend on an upstream depression (syphoning caused by a loss of pressure in the distribution network, for example in case of excessive collection) or on a downstream overpressure (caused by a pressure increase in the private network).
Backflow prevention in public grids is regulated by international standards. The UNI EN 1717 European standard provides for the use of backflow preventers upstream of heating and cooling systems, air treatment systems, hospital applications, irrigation, zootechnical, food and fire-prevention installations.
The EN 1717:2000 standard on prevention of backflow pollution classifies the water contained in systems (according to the degree of riskiness for human health) and the related backflow preventers more suitable.
Category 1: Drinking water supplied by the distributor.
Category 2: Fluid with no risk for health, such as in 1, which qualities have been compromised after changing its temperature, taste, odor or aspect. Examples: domestic hot water; stagnant water.
Category 3: Fluid with a specific risk for health caused by the presence of harmful substances. Examples: water of centralized heating systems with no additives; water from dish and utensil rinsing; toilet tank water.
Category 4: Fluid with a high risk for health caused by the presence of one or multiple “toxic or highly toxic substances, or one or multiple radioactive, mutagen or cancerogenous substances. Examples: sweetened water not for human consumption; water + anticorrosion additive not for human consumption; water + antifreezing additive; water + algicide.
Category 5: Fluid with a high risk for health caused by the presence of microbiologic or viral elements. Examples: sewer water, refluent water; water for personal hygiene; toilet water.
