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Dredge Obstruction
If you notice that there is an obstruction on the bottom part of the jet, the water will keep on flowing to the sluice however you will be able to notice that it is not as strong as it normally would be. The water that flows through the sluice will only have a little bit or no gravel at all in it. Depending on what amount of the suction tube has been blocked, the suction that is supposed to occur at the nozzle will not be really good and in some cases might stop all together.
The answer for these two types of obstructions is to clear out the suction tube by getting rid of the obstruction. This in most cases can be done by getting it to be in the same position it was when it went inside the tube and allowing it to be taken over to the pressure box.
This is not a difficult thing to do if the obstruction is located inside the suction nozzle or the flexible part of the tube. All you have to do is lift the suction nozzle underwater until it is pointing upwards. If this is where the obstruction has occurred, you will normally be able to see it and should be able to move it with a little stick. If the obstruction is in the flexible part of the tube it can be situated in a different place by lifting the tube and twisting it softly to a certain area. If this does not turn out to be successful you can try tabbing the tube in different areas along the length and observe if the vibration causes the obstruction to move.
If the obstruction is located close to the suction tube hole past the base of the jet, it will need to be taken out from the other end. You should be able to find a plug in the pressure box since most dredges have them. All you need to do is remove the plug and place a long rod inside and poke down at the ejector. If you see a surge of water and gravel you will know that the obstruction has been moved out.
When you are trying to get rid of either type of obstruction it is better to have just water sucked in through the suction tube. If you leave the nozzle in an area where gravel can get sucked in, the smaller stones will build up behind the obstructions and will cause there to be a great deal of plugging in the tube and cleaning it up and taking care of this type of situation will require of a great deal of work.
If the two last procedures did not work in resolving the obstruction problem, the next thing you can do is turn off the dredge and disconnect the suction tube from the ejector and remove the obstruction manually. When doing this you should not use a stick that is longer than the ejector tube; this is recommended because otherwise in most cases the suction tube gets punctured on one side. It is not always an easy thing to repair a suction tube and if the job is not done very carefully you can ruin a good many feet of expensive tubing in just one wrong move.
