The VHP39 unloader from Water Cannon is machine-forged and constructed with a brass valve body and a stainless steel ball and seat for trouble-free operation. It manually adjusts from 100 up to a maximum of 5,650 psi via an adjustment knob that has a tamper-resistant setting. The unloader includes a built-in easy-start feature that allows starting without any static back pressure when mounted in a vertical position. It automatically sends the water into a bypass loop when the water flow is stopped at the trigger gun, allowing for safe release of pressure at the pump head. 800/333-9274; www.watercannon.com.