Hose pumps work by alternately compressing and relaxing a specially designed resilient hose. The hose is compressed between the inner wall of the pump housing and the compression shoes on the rotor. A lubricant is used to reduce heat and wear on the hose. The pumped sludge comes in contact with the inner wall of the hose, which cushions entrained abrasives during compression. As a positive displacement pump, the pump output is directly proportional to speed at either high or low discharge pressures.