This Pressure Regulating Unloader is designed for single gun or pump operation. This unloader maintains set system pressure and goes into by-pass with the release of the trigger or an obstruction downstream. The pressure sensitive feature permits a wide range of flows and quickly resumes full pressure when the gun is opened or the obstruction cleared. It is recommended for intermittent cleaning applications. It is NOT recommended for weep systems. 5-10% by-pass is necessary for optimum performance (blue spring).