I used alloy for weight reasons, but also because it was what I had on hand. I lined up the new 3/4 inch jet to be slightly pointing downward but up the center of the pipe - so the water jet would hit the bottom of the pipe about 3 or 4 feet up. Mostly because my hand wouldn't fit up past the nozzle restriction. The old shop bought venturi had worn totally out and was very hard to get jammed rocks out of. My pump is a 5 hp Honda driving an Onga pump - a factory built pump/motor unit available here in NZ. The last one was four inch and I used a 3/4 inch jet with a flare out to the 1 1/2 inch supply. Sorry the site will not let me attach a picture of the suction nozzle.Hi there, I have made a few suction venturi nozzles over the years, as I couldn't find or couldn't afford store bought. I have a Honda GX engine driving a Koshin pump which will deliver 240 GPM.īeing a commercial diver I have always used large diameter underwater air lifts supplied with large compressors which move massive amounts of sea bed, I am hoping this dredge will move a decent amount of material. I am thinking of a 4 inch suction pipe supplied from a 2 inch pressure hose same as in the photo but I am wondering will I have to reduce the diameter of the pressure pipe as it enters the suction pipe, I am sure I have read somewhere that the reduction should be approx times 4 so that would make the reduction diameter at 1/2 inch as it joins the suction hose.

So I am looking at getting one made from a local blacksmiths at short notice.

First post on this very interesting and informative site, I'm looking for a some advice from the experienced dredging people on this site, I am from England and am looking to remove a considerable amount of sand and small pebbles/rocks from the seabed at approx 30ft depth, I was looking at buying a 4 inch suction nozzle from an ebay site based in the USA (photo below) but as this job will be coming up in the next week, the delivery time is too long.

4 inch dredge nozzle