An axial pump operated in a standing manner has an inner housing part (2), in which a shaft (10) carrying a propeller wheel (4) is mounted. An outer housing part (1) is provided, wherein a flow path (3) for the fluid delivered by the propeller wheel (4) is formed between the inner and outer housing part. The inner housing part (2) is designed for receiving a fluid buffer for at least one seal (15) and includes an opening (19, 20) for the supply and drainage of the buffer. A recess (24, 25) is provided in the outer housing part (1), via which recess the opening (19, 20) is accessible from the outside. A valve (23) is provided in or on the inner housing part (2), with which valve the conduit leading through the opening (19) can be blocked.