工作原理：Operation principle
市政饮用水从第一级止回阀进入，经过排污器、二级止回阀，向下游供水，一部分介质由导管进入排污器膜片下腔，使排污器阀瓣关闭。当市政管网停水，进口压力消失，一、二级止回阀关闭，同时由于导管不再向排污器膜片下腔供给压力，排污器的阀瓣在弹簧力和一、二级止回阀间介质压力作用下而打开，把两止回阀间回流的介质排放掉，这样起到防污隔断作用，即使第二级止回阀出现内漏，回流的介质也会经排污器排到外面，而不会流进主管网。一旦主管网压力恢复正常，排污口阀瓣受压关闭，一二级止回阀打开，主管路恢复向支管供水。
Municipal drinking water enters from the first level check valve, passes through drainage device, second level check valve, to supply water to the water downstream, part of medium enter the lower cavity of diaphragm of drainage device, to close the valve flap of drainage device. When the municipal water supply network stops, the pressure of inlet disappears, first, second level check valves close, at the same time, because the conduit do not supply pressure to the lower cavity of diaphragm of drainage device, the valve flap of the drainage device opens under the force of spring, as well as the pressure between the first, second level check valves, to discharge off the backflow medium between the two check valves, so as to play the role of anti-pollution and isolation, even if the second level check valve occurs leakage, the backflow medium will also be discharged outside, and will not flow into the main network. Once the pressure of the main network returns to normal, the valve flap of drainage outlet closes under pressure, first, second level check valves open, the main network return to supply water to branch pipeline.
8.安装：installation
8.1 安装时核对阀门性能参数是否与使用工况相符。
When installation should check whether performance parameters of valve is consistent with the operating conditions.
8.2 本阀必需水平安装，必需注意阀体上的流向箭头要与介质流向一致。
The valve must be installed horizontally, must pay attention that the direction of flow arrow is consistent with the direction of medium.
8.3 安装地域应设有排水设施，保证防污隔断阀不被水淹没。最好将试验球阀出口和排污口接排水管。
The installation area should set drainage facilities, to guarantee the anti-pollution  isolating valve will not be submerged in water. It is preferable to connect outlet of test ball valve and drainage outlet with drainage pipeline.
8.4 阀前应装闸阀（或蝶阀），过滤器及橡胶软接头（伸缩器），阀后安装闸阀（或蝶阀）。
On the front of the valve should install gate valve (or butterfly valve), filters and soft rubber joints (expansion bend), on the back of the valve should install gate valve (or butterfly valve).
8.5 阀门安装好后，通入正常压力的水，排污口应无水流出。此时缓慢将试验球阀完全打开，    这时排污口有大量水排出，关闭试验球阀，排污器也随之关闭，这说明防污隔断阀动作正常。如果主管网不经常发生停水现像，也可定期（一个月左右）用此方法来检验阀门是否工作正常，并可借此排除阀内沉淀的杂质。
After installation of valve, access to water with the normal pressure, the drainage outlet should have no water leakage. At this time, slowly open the test ball valve completely, then a lot of water is discharged at the drainage outlet, close the test ball valve, the drainage device closes too, this shows that action of anti-pollution isolating valve is normal. If the main pipeline network does not often occur water suspension, also can check whether the valve works normally periodically (about a month) using this method, and may to remove impurities in the valve.