(1) Open the inner blow-off valve;
(2) the external blow-off valve is opened very slowly, the pipeline is preheated and the sewage is discharged;
(3) opening and closing the external sewage valve many times, slowly washing out the liquid dirt in the furnace tank, so that the liquid dirt can be discharged;
(4) close the inner discharge valve and drain the residual water between the two discharge valves; (5) close the external discharge valve and end the discharge of sewage.
