If you're wondering how a highbanker can literally suck up gravel from the bottom of a stream without the gravel going through the pump and destroying it, it is because of a handy device called a suction nozzle or power jet nozzle. These devices convert the pressurized water discharged from the pump into a vacuum.
Generally speaking, a dredge that is designed to work with the sluice on a stand, in shallow water, is almost always equipped with a suction nozzle. A dredge designed to work on flotation, with highbanker hopper a compressor for underwater dredging, is almost always equipped as a power jet. Since a power jet and supply hose must be kept under water at all times, it won't work very well in shallow water. Shown below is a wide variety of gold dredge nozzles from several reputable manufacturers.
Gold can hide down in the deepest part of a crack or crevice or behind a boulder and often is best reached with a hand dredge, also called a "sucker gun" or "suction gun. " This gold prospecting tool is ideal for working below the water line when a motorized dredge cannot be used. Legal for gold wash plant prospecting in California! There are NO legal issues with using a hand- operated device, and since it helps you get the gold out of some really tight spaces, a hand dredge is well, handy, when you're prospecting along a river. If you've found a rich spot that is hard to access, the hand dredge can produce some decent gold!