A seal for a fluid level sensor assembly mounted in a pipe includes a seal body arranged to be sealingly fitted around a sensor, the seal body having a first side defining a first lip and a second side defining a second lip, the second lip being thinner than the first lip, and a spring mounted to the seal and arranged to move the seal body along the sensor, when mounted around the sensor, such that the second lip provides a seal around the sensor and the first lip wipes the sensor to remove debris thereon.