Removal device for removing dirt particles from a liquid in a liquid conduit system the removal device comprising: - a main channel for a main flow, the main channel having an entry and an exit which are configured to be connected to the conduit system, wherein the entry and exit comprise thread for coupling to the conduit system, - a housing which defines an inner space, wherein in top view, the housing has a substantially circular form, wherein at a bottom end of the housing, a dirt discharge with an opening and closing mechanism is provided for discharging dirt particles, wherein the housing is elongate in the vertical direction, i.e. the housing has a height which is greater than a diameter of the housing, - at least one supply channel (36A,36B) extending from the main channel to the inner space, wherein the at least one supply channel branches off from the main channel at a branch-off location, and wherein at the branch-off location a local widening part of the main channel is provided which extends substantially around the main channel, the local widening part being constructed to guide an outer part of the main flow which flows through the main channel into the local widening part and subsequently into the at least one supply channel, wherein directly downstream of the local widening part a local narrowing part of the main channel is provided having a sharp edge which is directed against the direction of the main flow, which narrowing part is constructed to guide an outer portion of the main flow into the local widening part, - at least one return channel extending from the inner space back to the main channel, directly or indirectly via a return chamber, wherein a distance between the branch flow entry and the return flow exit measured along the main flow channel is less than twice the diameter D of the main flow channel, - a quiet zone in the inner space in which in use the liquid has a substantially smaller velocity than in the main channel, the quiet zone being configured to allow dirt particles to settle at a lower end of the housing, wherein the housing is connected at an upper region thereof to the main channel via a coupling, wherein an exit of the supply channel into the inner space and an entry of the return channel from the inner space are provided in an upper region of the quiet zone, and wherein the quiet zone comprises a lower region in which settling of dirt particles occurs. - a main channel for a main flow, the main channel having an entry and an exit which are configured to be connected to the conduit system, wherein the entry and exit comprise thread for coupling to the conduit system, - a housing which defines an inner space, wherein in top view, the housing has a substantially circular form, wherein at a bottom end of the housing, a dirt discharge with an opening and closing mechanism is provided for discharging dirt particles, wherein the housing is elongate in the vertical direction, i.e. the housing has a height which is greater than a diameter of the housing, - at least one supply channel (36A,36B) extending from the main channel to the inner space, wherein the at least one supply channel branches off from the main channel at a branch-off location, and wherein at the branch-off location a local widening part of the main channel is provided which extends substantially around the main channel, the local widening part being constructed to guide an outer part of the main flow which flows through the main channel into the local widening part and subsequently into the at least one supply channel, wherein directly downstream of the local widening part a local narrowing part of the main channel is provided having a sharp edge which is directed against the direction of the main flow, which narrowing part is constructed to guide an outer portion of the main flow into the local widening part, - at least one return channel extending from the inner space back to the main channel, directly or indirectly via a return chamber, wherein a distance between the branch flow entry and the return flow exit measured along the main flow channel is less than twice the diameter D of the main flow channel, - a quiet zone in the inner space in which in use the liquid has a substantially smaller velocity than in the main channel, the quiet zone being configured to allow dirt particles to settle at a lower end of the housing, wherein the housing is connected at an upper region thereof to the main channel via a coupling, wherein an exit of the supply channel into the inner space and an entry of the return channel from the inner space are provided in an upper region of the quiet zone, and wherein the quiet zone comprises a lower region in which settling of dirt particles occurs. wherein the housing is connected at an upper region thereof to the main channel via a coupling, wherein an exit of the supply channel into the inner space and an entry of the return channel from the inner space are provided in an upper region of the quiet zone, and wherein the quiet zone comprises a lower region in which settling of dirt particles occurs.