| 摘要 |
The invention relates to a backflow preventer having a housing, which has an inlet opening, an outlet opening and at least one leakage opening disposed between these openings and accommodates first and second nonreturn valves disposed in series, the first nonreturn valve being held displaceably in order to open up and close a flow connection between an intermediate space of the housing and the leakage opening. To develop the backflow preventer in such a manner that an inadmissible increase in pressure in the region of the outlet opening can be avoided in a structurally simple way, according to the invention it is proposed that the housing comprises an inner housing and an outer housing, the outer housing having the at least one leakage opening and the inner housing accommodating the two nonreturn valves and being held such that it can be displaced to and fro in the direction of through-flow within the outer housing, and the inner housing having an outlet opening, via which the flow connection between the intermediate space and the leakage opening can be produced independently of the position of the inner housing, by displacement of the first nonreturn valve relative to the second nonreturn valve.
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