This Specification sets out requirements for a pressure dependent stack vent valve that is installed in the open to atmosphere stack piping. The prime function of the fitting is to minimise heat losses by management of air flows through the stack to the atmosphere. Note: There is no energy efficiency performance criteria for these products as this is dependent on the installation and climatic conditions. The Plumbing Code of Australia (PCA) requires that most products intended for use in plumbing and drainage installations in or around buildings to be evaluated and certified to WaterMark product specifications. WaterMark certification to an applicable product specification provides a process to evaluate and authorise products to enable their use in a plumbing and drainage installation. Thus ensuring that the plumbing and drainage products are fit for purpose for which they are intended. This WaterMark Technical Specification (WMTS) was prepared in accordance with the Manual for the WaterMark Certification Scheme, Appendix 4, Protocol for Developing Product Specifications. The objective of WaterMark Technical Specification is to enable product certification in accordance with the requirements of the Plumbing Code of Australia (PCA).