本发明涉及与具有入口开口，出口开口和泄漏开口，并且所述第一壳体中的止回阀，并且容纳第二止回阀，其被布置在另一，后面一个，其中，在一个释放位置和一个阻挡位置来回之间的壳体的第一止回阀 通过移动第一止回阀，在外壳内部的两个止回阀和泄漏开口之间布置的流动连接件可释放或可锁定。 为了开发该止回阀使得第一止回阀的倾斜的危险可被减小，本发明提出的阀壳体具有在外侧两个相互间隔开的环形槽，在其中的每一个的密封环布置。

The invention relates to a non-return valve with a housing having an inlet opening, an outlet opening and a leakage opening and having a first and a second check valve receives, which are arranged one behind the other, wherein the first check valve in the housing between a release position and a blocking position to and fro is held, and by moving the first non-return valve a flow connection between an arranged between the two check valves interior of the outer housing and the leakage opening is releasable or lockable. In order to develop the non-return valve such that the risk of tilting of the first non-return valve can be reduced is, the invention proposes that the valve housing on the outside has two mutually spaced annular grooves, in which is arranged in each case a sealing ring.