Filtering device and water heater circulating system

The invention discloses a filtering device and a water heater circulating system. The filtering device comprises a shell, a filtering part, a power part and a cleaning part, and the power part is pushed by fluid to drive the cleaning part to rotate; the cleaning part is used for washing the filtering part; the filtering device further comprises a pressure difference deformation part, and a first linkage part and a second linkage part which are correspondingly arranged; the pressure difference deformation part moves under the action of the pressure difference between the fluid pressure inside the filtering part and the fluid pressure outside the filtering part, so that the cleaning part is switched between a rotating state and a stopping state; when the cleaning part is in a rotating state, the pressure difference deformation part drives the first linkage part and the second linkage part to be in transmission connection, and the power part drives the cleaning part to rotate through the first linkage part and t