What does the symbol refer to?

The symbol in question represents an eccentric reducer, which is a fitting used to connect pipes of different diameters. The defining characteristic of an eccentric reducer is that it has one side that is aligned and level with the existing pipe, while the opposite side tapers down to connect to the smaller diameter pipe. This alignment is particularly beneficial in applications where maintaining a level flow is crucial, such as in drainage systems, as it helps prevent air pockets from forming and ensures that the flow remains consistent.

In contrast, a concentric reducer, which is also a type of pipe fitting, has a symmetrical shape, tapering down uniformly from a wider diameter to a narrower one around a central axis. A check valve, on the other hand, is a type of valve that allows fluid to flow in one direction only and is not used for resizing pipes. Additionally, a P-trap is a plumbing fitting designed to prevent sewer gases from entering buildings by trapping a small amount of water in a bend. Understanding these differences is essential in recognizing the specific application of each fitting in plumbing and piping installations.