Preface: This volume contains the seventh edition of CSA B64.10, Selection and installation of backflow preventers, and the fourth edition of CSA B64.10.1, Maintenance and field testing of backflow preventers. The two Standards are intended as a guide for designers of potable water supply and plumbing systems in the selection of the proper type of device, for installers and owners in the installation and maintenance of the devices, and for inspection authorities in the testing of the devices after they have been installed. The Standards provide information on other methods of preventing contamination of potable water by backflow from back siphonage or back pressure. CSA B64.10 and CSA B64.10.1 provide selection criteria, installation and maintenance procedures, and techniques that represent the general state of the art, but should not be construed as all-inclusive, especially where procedures and techniques are altered to meet special conditions. Where there are problems with a specific installation, it is suggested that the manufacturer of the backflow preventer be consulted.