The acid and alkali resistant self-priming pump does not need to add water when the self-priming pump is started. It relies on its own impeller to drive the transmission of liquid medium in the pipeline. The larger the seal clearance of the impeller, the lower the self-priming height. This does not mean that the self-priming pump does not need to add water. After the self-priming pump is installed for the first time, it is still necessary to fill water by using the impeller of the self-priming pump to suck up water. Several problems need to be noted, such as less water diversion, loose screws at the inlet and outlet covers of the self-priming pump, insufficient tightness of the inlet pipe, and small suction head of the self-priming pump. Check whether the physical structure or accessories of the acid and alkali resistant self-priming pump are damaged, and whether there are foreign matters inside the self-priming pump, such as weeds. When the self-priming pump has water output but the water output is not large, first check whether the clearance between the lower impeller and the shell mouth ring is too large.