The volume of a mechanical strain washer is expressed in gallons or liters per minute,[1] typically designed into the pump and never variable. The stress, expressed in kilos per sq. inch, pascals, or bar, is designed into the pump but can be diversified by adjusting the unloader valve or using specialized nozzle suggestions. Machines that produce pressures from 750 to 30,000 psi (5 to 200 MPa) or extra can be found.