A Y strainer, not surprisingly, is shaped like the letter Y. One end is removable so the strainer can be cleaned. This particular type of strainer is used with pressurized gas or liquid lines where only minimal amounts of solid materials are expected.
Rust and scale are trapped by a Y strainer in hot water systems. Typically, a Y strainer is installed immediately prior to the hot water circulating pump. This prevents particulates from entering the rotor of the pump, which could cause problems. Ideally, a Y strainer should be installed in such a way that allows the strainer to be cleaned without having to drain the whole system.