The flip side of fresh potable water going into a facility or structure is the waste water or sewer output. These lines collect all the waste fluid and solids and direct them to a sewage treatment plant. These treatment plants feature a lot of low pressure piping and valves to perform their “dirty work.” The requirements for waste water valves in many cases is much more lenient than the requirements for clean water service. Iron gate and check valves are the most popular choices for this type of service.