What does the symbol refer to?

The symbol in question refers to an eccentric reducer. Eccentric reducers are used in piping systems to connect two different pipe sizes while allowing for a smooth transition of fluid flow. Unlike concentric reducers, which have a symmetrical profile, eccentric reducers are flat on one side, allowing for an offset change in pipe diameter. This design helps to maintain the elevation of the pipeline and can prevent air pockets from forming, which is especially beneficial in horizontal piping systems.

In piping design, understanding the specific applications and differences between eccentric and concentric reducers is essential for ensuring proper fluid movement and system functionality. The other options such as concentric reducers, check valves, and P-traps serve different purposes in piping systems, making it crucial to identify the correct symbol to use in the context of fluid flow management.