Unloaders are typically designed for a single gun or single pump operation. The unloader maintains a set system pressure with the trigger gun open and goes into by-pass with the release of the trigger. Unloaders take the pressure of the pump head when in by-pass mode. Not really recommended for weep systems and for optimal performance 5-10% in by-pass is recommended.
Pressure Regulators are designed for a single or multiple pump, weep or multi-nozzle systems. A regulator maintains set system pressure even when only one of several guns or nozzles is performing by-passing the unused flow. Regulators allow just enough liquid to flow through to maintain system pressure when in by-pass mode. 5-10% in by-pass is recommended for optimal performance.