A graffiti removal system from a surface to be cleaned, wherein said system comprises a container for liquid, a first pump for pumping liquid from said container to a discharge unit connectable to the first pump for discharging pumped liquid onto the surface to be cleaned, wherein said discharge unit comprises a cover member defining an interior space and an opening through which liquid is dischargeable from said interior space onto the surface to be cleaned, wherein one or more nozzles are provided within said interior space for discharging liquid pumped by said first pump, wherein a circumferential portion of said cover member is provided with a resilient spray guard configured for sealing against the surface to be cleaned, and wherein the system further comprises a second pump connectable to an outlet port of the discharge unit for pumping air and liquid from said interior space and out through the outlet port; wherein the system further comprises a filtering device configured to filter the liquid pumped from the discharge unit by the second pump and subsequently supply it to the first pump wherein the filtering device is characterized in that comprises a first chamber for dirty liquid and a second chamber for clean liquid, wherein the cleaning system is configured to route liquid pumped from the discharge unit by the second pump into the first chamber, wherein the filtering device comprises at least one primary filter and a third pump configured to pump liquid from the first chamber through the primary filter and into the second chamber, wherein the filtering device comprises at least one secondary filter and a fourth pump configured to pump liquid from the second chamber through the secondary filter and back to the second chamber, wherein the cleaning system is configured to supply the first pump with liquid from the second chamber, and wherein the at least one primary filter comprises a mechanical particle filter, and wherein the at least one secondary filter comprises a chemical filter comprising active coal. a container for liquid, a first pump for pumping liquid from said container to a discharge unit connectable to the first pump for discharging pumped liquid onto the surface to be cleaned, wherein said discharge unit comprises a cover member defining an interior space and an opening through which liquid is dischargeable from said interior space onto the surface to be cleaned, wherein one or more nozzles are provided within said interior space for discharging liquid pumped by said first pump, wherein a circumferential portion of said cover member is provided with a resilient spray guard configured for sealing against the surface to be cleaned, and wherein the system further comprises a second pump connectable to an outlet port of the discharge unit for pumping air and liquid from said interior space and out through the outlet port; wherein the system further comprises a filtering device configured to filter the liquid pumped from the discharge unit by the second pump and subsequently supply it to the first pump wherein the filtering device is characterized in that comprises a first chamber for dirty liquid and a second chamber for clean liquid, wherein the cleaning system is configured to route liquid pumped from the discharge unit by the second pump into the first chamber, wherein the filtering device comprises at least one primary filter and a third pump configured to pump liquid from the first chamber through the primary filter and into the second chamber, wherein the filtering device comprises at least one secondary filter and a fourth pump configured to pump liquid from the second chamber through the secondary filter and back to the second chamber, wherein the cleaning system is configured to supply the first pump with liquid from the second chamber, and wherein the at least one primary filter comprises a mechanical particle filter, and wherein the at least one secondary filter comprises a chemical filter comprising active coal.