Using the Suction Gold Dredge:
 These are the best Gold mining machines to use when processing larger amounts of stream or river gravel for a small scale production operation. If you have enough flowing water and regulations allow this is a great option for sampling and mining. When I refer to the intake size, it is the diameter of the inside of the nozzle, which feeds into the hose. Interestingly, some states (e.g. California) consider the dredge size to be the diameter of the restricting ring on the nozzle tip, hence a manufacturers 5 inch Gold dredge is considered a 4 inch Gold dredge by DFG (Department of Fish and Game) regulations (2008). This fact is handy to know, so it pays to read the regulations carefully and know your equipment. The suction hose is attached to the intake suction nozzle on one end and the jet flare tube on the other. An engine powered pressure jet nozzle on this tube creates a suction in the larger dredge hose. This sucks the dirt, gravel and smaller rocks from the operator's suction nozzle through the hose to a sluice box fixed to the pontoons on both sides to float the dredge.
A larger intake hose to nozzle restrictor ring diameter helps prevent rock jams. A rock jam is a time and energy consuming event that plugs up the suction hose until it is cleared. To prevent jams, watch the size of material you put the nozzle next to. If the rocks have any dimension near the diameter of the hose then use your hands to move these larger rocks. Experience will help with knowing just how big is too big. Usually a gentle tap with a blunt rock will dislodge the jam. Be careful not to damage your suction hose. I use a rubber mallet to avoid damage to the suction hose and my hands. Big rocks uncovered by dredging must be moved carefully by hand downstream out of the way of the upstream progressing dredge hole the nozzle operator makes. Remember, watch those rocks and fingers near the nozzle, rock pinches hurt! Also watch for Gold flakes or nuggets as you progress near bedrock or clay deposits. You want to advance your suction dredge nozzle along these gold lines or gold leads carefully.
It pays to monitor the rate at which you suck up placer Gold material with your suction dredge. You want the riffles to keep filled but not over fill. There should always be about 1/2 to 3/4 inch of exposed carpet or miner's moss just before the next riffle in the sluice. The front part of the riffle must remain covered in sand and pebbles to keep the Gold trapped while moving lots of rocks and gravel through the nozzle. A good Gold dredge nozzle operator will always keep a bit of sand and gravel flowing even while pausing to look at the rock situation. That extra layer of material will keep your fine and coarse Gold from blowing out the back of the dredge and still provide the production rate required to move enough placer material to get the nuggets. If fine Gold is present slow that throttle down and catch every ounce.
It is important to set up your gold dredge so that the riffles fill properly for the rate at which you plan to operate. Spend a few hours experimenting with the angles and distances you set your adjustment plates and sluicebox to dredge pontoon angle and try using the settings at different throttle settings. Watch for sluicebox riffle over or underload! Use trial and error to learn the right settings for high, medium and low dredge pump flow rates into your sluicebox. Do this experiment before you strike it rich(er)! The payoff is in capturing better black sands and more flood gold and yet retaining more material moved per hour. Gold production will be best when you optimize for both characteristics and get a feel for how to vary based on visual appearance of the material your dredge is sucking up.
When it comes time to clean up the Gold dredge's sluicebox try a rectangular "Rubbermaid" tub that is a bit wider than the Gold dredge sluice box end. Get the dredge to water shallow enough to place the tub just below the end (try a tailings pile) or get help to balance. Watch out it will be heavy if you use a larger 4 to 6 inch dredge. Some manufacturers (e.g. Keene engineering) make special buckets and holders for this purpose if you prefer.
Caution! Remember to watch out for those boulders and unstable rocks as you expand your sample hole wider and deeper. Dredging underwater means you must keep your dredge hole and surrounding environment safe at all times. As the hole gets deeper keep widening the top layers to prevent side walls from collapsing on you. Be alert and "If in doubt, move it out!"
My Personal Favorite Gold Prospecting Reference Book
Gold Prospector's Handbook available from BlackCatMining,
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The Full Line of Proline Suction Gold Dredges!
Gold Dredge Size & Type
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Dredge Pros
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Dredge Cons
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| 2 inch – backpack dredge:
.5-2 cubic-yd/hr |
Light and easy to pack in and out of the location. Good for prospecting and sampling. With suction nozzle it can be used in very shallow water.
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Cant move much material so dredging is harder to do if you want to move a lot of sand and gravel. Not good for production.
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| 3 inch – Sampling dredge:
1-3 cubic-yd/hr |
Still lighter and smaller than a 4 inch and can move a lot more material than the 2 inch.
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Still low on production for a serious operation. Portability is pretty good for remote places.
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| 4 inch – Sampling/small scale production dredge
1-4 cubic-yd/hr |
The smallest of the production dredges but still good at sampling for pay streaks.
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A bit harder to lug around, it is heavier and more work to put together and take apart. Fairly mobile still, this makes it good for more remote sites.
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| 5 inch – larger scale sampling/production dredge
2-10 cubic-yd/hr |
Good for larger operations and can move more dirt than all the other smaller dredges. Still good for sampling but on a larger scale. Hose is flexible and can be operated by a single dredger.
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Heavier to disassemble and move around. May have multiple or larger engines.
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| 6 inch – a good dredge for the serious prospector/smaller commercial production dredge
6-15 cubic-yd/hr |
A useful size for someone who has found a sizable pay streak and wants to get all the gold out that you can.
You can move rocks gravel and sand up to about 5 inches across without a plug up of the hose or jet.
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Larger nozzle makes it harder to sample with, although you still can sample larger rivers to locate gold in bigger areas.
This hose isn't as flexible as a smaller dredge although one person can handle it well enough for production. Two man teams are better because the rocks are uncovered so quickly by a 6" unit that a single dredger can be overwhelmed with the work of clearing of large cobbles and small boulders that don't fit in the suction nozzle.
Can have multiple engines or engines in the 15-20 Hp range. This is a heavier beast to haul. Be ready for 2 or more assistants.
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8 inch – a commercial dredge designed to process large amounts of sand, gravel and rock.
10-30 cubic-yd/hr |
For commercial operations this is a good size. It can suck up quite a lot of rocks, gravel and sand and in a short period of time.
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For the recreational prospector looking for the fun of the outdoors and the reward of finding gold, this is not the right size.
It is typically used for commercial projects. Manning the hose and moving the rocks that an 8" dredge will need at least two men to make productive use.
Dredges this size are legally limited in which waters they can be used.
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| 10 to 12 inch – definitely a commercial dredge
20-50 cubic-yd/hr |
Good for larger commercial operations. Moves a lot of rocks, gravel & sand allowing for greater quantity's of gold to be collected.
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Commercial dredge only. A lot of work to keep running and to move around.
Lot's of rocks to move, needs a team of underwater worker$.
See 8" limits above
Can you say 80+ hp VW engine!
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