Abstract: A backflow prevention apparatus has a housing with an opening having a predetermined length. A first valve body, and a second valve body may be slidably sealed with one another, and compressed such that their combined length is less then the length of the opening. In the compressed state the valve bodies may be inserted within the opening of the housing and then elongated such that the ends of valve bodies engage and sliding seal with segments of the housing. A spacer may be placed between the first valve body and the second valve body to secure them within the opening. An intermediate valve body may be introduced between the first valve body and the second valve body.

Abstract: A backflow prevention apparatus has a housing with an opening having a predetermined length. A first valve body, and a second valve body may be slidably sealed with one another, and compressed such that their combined length is less then the length of the opening. In the compressed state the valve bodies may be inserted within the opening of the housing and then elongated such that the ends of valve bodies engage and sliding seal with segments of the housing. A spacer may be placed between the first valve body and the second valve body to secure them within the opening. An intermediate valve body may be introduced between the first valve body and the second valve body.

Abstract: A check valve for preventing backflow in a conduit. The check valve includes a check valve mechanism having a valve seat defining an opening for fluid flow, a seal retainer positioned downstream of the valve seat and configured to seal the opening and a linkage between the valve seat and seal retainer. The linkage permits guided axial displacement between the valve seat and the seal retainer. The linkage also provides a retention force urging the seal retainer into engagement with the valve seat and creating a fluid seal therebetween when a downstream flow in the opening is insufficient to overcome the retention force provided by the linkage.