Abstract: A single-acting slide sealing for a liquid pump or similar. The sealing comprises a rotating counter ring (8) to be fastened to a rotating machine part (2) and a non-rotating sealing ring (9) to be supported on a stationary machine part (1). The sliding surface in the counter ring is sealingly pressed against the sliding surface in the sealing ring. The sliding surface in the sealing ring (9) is provided with a weakened part (15) which, through a channel (14) in the sealing ring, is in flow connection with a leak indicator (17), such as an electrical or mechanical indicator instrument (21), which, when the weakened part is worn through, is activated by the action of liquid entering into the channel and in advance indicates that the sealing ring is worn and must be replaced.