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#394232 12/08/14 04:11 PM
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Has anybody every used, bought or rented one of these before?

http://www.piranhapumps.com/mini_dredges.html

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Tim, it is just a trash pump on pontoons with a weighted suction hose. I do a little dredging with my spray barge, but you take out a LOT of water with the sediment and depending on your pond size, you need a lot of discharge hose to pump it below the dam. Pumping it anywhere above the pond just circulates the sediments.



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I can take a lot of water out. The area that's silting and muddy is pretty shallow compared to the main portion of the pond which is 23' deep. I have a steep bank on one side for the discharge of the mud/silt/sand. Do you think a large trash pump will do it? I have a means to float the pump if needed.

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A 3" trash pump with a heavy (30#), V shaped drag style suction setup with holes drilled at the max solids capacity of your pump can move quite a bit of silt... Making a cage to prevent clogging can save cleanout time...it WILL clog up the suction holes often with leaves.



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I removed leaves first with a setup using a 4 foot long section of 4" PVC with 6" squares cut out to reduce suction. It allowed leaves to enter without pulling in rocks over 3/4" in size....one big rock sucked in at full throttle can destroy your pump impellor fast!



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Is there a gold dredge type suction system that would work where you don't run the solids through the pump?

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They make air lift dredges. Google should have lots of links

Diver Cody uses an air powered dredge all the time. You might ask him.

Last edited by Bill D.; 12/08/14 05:36 PM.

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You can also build a siphon system that will handle anything as large as your smallest pinch point in the system, which is what the gold dredges we see on TV are using. They get very pricey, fast on the hoses, and are not all that mobile though.

Last edited by Rainman; 12/08/14 05:35 PM.


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Have any suggestions for building one myself? Something like a 4" trash/mud pump with venturi/siphon nozzle setup?

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Do you have access to a good air compressor that can put out a decent amount of CFM? What is the water depth that you would like to suck out?

I have to get on shift answer these questions and I think I can come up with something on the cheap for you that should function fine.

Also any large rocks or other debris to worry about?


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I do have a pretty decent 220V/200Gal air compressor about 100' from the pond. It will run large blast cabinets and still cycle off.

There is a 220V/1.5 hp water/fountain pump (pool type) that's in a pit next to the pond too. It supplies water to the pond fountain and/or watering lines throughout the yard.

I also have a Honda powered 2" trash pump and a 300 gallon water tank. I'm willing to get a 3 or 4" pump if needed.

The water depth I want to dredge to is no more than 6'. Most places less. I need to remove from 10" to 4' of muck in some of these areas. The water depth to the muck now in some areas is 1.5 to 2' deep at it's shallowest points.

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That water depth is going to be troublesome for a true airlift(However we have used them in as little as 4' of water but we use very large roto-screws like Ingersoll Rand 375 XP's: Which can put out around 300 to 400 something CFM). I would stray away from using a water driven pump as it almost always has an impeller of some type and for suction purposes even muck/sand will start to mess with the internal bearing and seals leading to premature wear. A trash pump can work I'm sure but you still would need to create either some sort of holding pool to let the sediment fall out of the water or a filtration system.

I'll look into some possible cheap setups for around $50-$100 or so tonight using materials you can use on other projects if it doesn't work out. I am assuming your compressor you mentioned probably only has small hand tool air sized hoses as in 3/8" or so also any sort of regulator in line to reduce line pressure? You said you have a 2" trash pump so do you already own a water discharge hose?

Anyways I'll try and respond yet tonight and send you a PM with a shopping list and if I can a quick sketch-up using excel or paintbrush or something.

The short story on what I'm thinking for your issue is probably going to be a 1 1/2" dia 6-8' section of PVC with two 90 degree fittings placed about 8" from the bottom to go through the side and then get the air heading back up the pipe (after reading this again that pipe diameter is to small for a double 90 turn see posts further on down for Rev.2 of the plan) going into say a 25' discharge hose that you can run up and over the bank or hopefully to someplace that the muck and water can go and drain and not go back into your pond. The air fittings you will have to choose yourself depending on what hoses you have for your current tank setup. Keep in mind going for max CFM's(Airlfow) here so bigger is usually better but no need to go overboard. I don't know 100% the rules on posting links to "Box Construction" stores so I'll send those on in the PM as well. Also by using the PVC pipe if you feel you want to try and suck more up at once(Be careful not to overload the system as you will then get clogs) You could just use a 3" to 1 1/2" reducer on the bottom like a vacuum cleaner attachment.

The only real limiting factors you are facing is compressor output in CFM and water depth. If you are feeling froggy you can always step up the pipe diameter you use just keep in mind trying to find a discharge hose for those larger diameters may take some searching and some cash.

Last edited by Diver Cody; 12/11/14 09:09 PM. Reason: Rev.2 New and Improved Design :)

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Air compressor wise, yes, 3/8" rubber line with regulator.

Will this system pump further than the 25' distance you mentioned with the discharge hose? I need to get it across the pond and over the bank to discharge into the woods.

I do have a second, even larger V-twin compressor in my back building I could possibly put on a trailer and run with a generator and use with my other compressor in parallel.

The 300-400 CFM you want with the air compressor is at what PSI?

Thanks again for all your help.

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No you don't need the 300-400 CFM I sent you that private message with supplies and things for a smaller version of the ones we use offshore. It will take a little longer but you will have more control and you won't be dredging up any of your hard layers unless you really try to. The PSI is one of those have to play it by ear things. Yes it can go further than 25' How far that I honestly can't tell you since every situation is different. How high of a bank are we talking about and how far across the pond does it have to go.

We made a system once that could literally suck up rocks that were weighing in the 100# range that they had put in and around a platform to combat scour and we were running those up and to a location 40' away. The further you have to move the material across water and land the more Flow you will require.

Hope this clears things up and answers your question some.

Also Check your messages the one I sent you answers a few of these questions and provides external links. So you can get a idea of what I'm thinking will work for you.

Alright sir I have to go get on shift for yet another 12-14 Hour day. If you still have anymore questions I'll check this thread later tonight.


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OK, got the message. Easy enough to put together, I'll give it a try, but like you said, I'm not sure about the lift and throughput it could have in such shallow water. I may ask my math buddies to do a quick calculation to see.

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As long as you can get it into deep enough water where when the unit is off the inlet part of the air introduction point is under about 2' of water it should be fine at the smaller diameter pipes. A cubic foot of freshwater at it's heaviest is at 62.4 LBS- 62 LBS depending on turbidity and temperature(Most calculations are based off the higher value), a cubic foot of seawater is 64 LBS. If you divide 64 by 144 you will come out with 0.44444 repeating indefinitely that is how much pressure one foot of seawater puts out in PSI per column foot. We use .445 PSI for all depth calculations or 33' = 14.7 = 1 atmosphere equivalent.

Freshwater is at it's heaviest 62.4/144= 0.43333 repeating indefinitely so at 6' wear your muck lies it should function fine till you start getting into really shallow depths then it will just be a fancy bubble maker. You are just creating slugs of air and water that have to be replaced as the bubbles cause the column of water to rise on top of it. With more slugs of air and water which the water will draw in from the bottom bringing with it the muck.

Hope this helps your math buddies if they want to run some quick calculations. But IMHO it should work out till you lose the water column above your inlet point. at which point you can cheat the system some and lay it down at a slight angle but always managing to have an uphill grade, as if you put it downgrade you once again just have a fancy bubble gun.

We are currently using one offshore on a project in 75 feet of seawater(FSW) to remove sand over a pipeline which is buried 9' deep for every foot we go down the pipe keeping an OSHA approved 3:1(3' in each direction for every 1' down) ratio we are removing about 9 cubic yards of material.

Anyways let me know if you decide to run with it and let me know if it work's if you do. Or hit me up if you have any more questions.

Have a good one sir.



For those who are curious what I sent him it was a shopping list and a link to an extremely basic airlift system I found on a site. As I didn't have time to make a mock up in excel.

http://www.mindspring.com/~divegeek/airlift.htm
(Really basic airlift design link)


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I would like to ask you to post the parts needed and also if you did a small drawing. I've asked the mods about this. They agree, since you are not personally selling, advertising, or endorsing a product/business.

We've had a little bit about small scale dredging before. I've tried it unsuccessfully with a semi-trash pump. A friend further discouraged me from doing it with a semi-trash pump, saying the grit in the silt/muck would quickly wear out the pump impeller. If I had a system I thought would work, I'd rent a trash pump for a day.

Ken


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ME TOO


Goofing off is a slang term for engaging in recreation or an idle pastime while obligations of work or society are neglected........... Wikipedia
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Here's what Diver Cody sent me;

Shopping List

1- 10' PVC pipe section 1 1/2"
http://www.homedepot.com/p/Unbranded-1-1-2-in-x-10-ft-PVC-Sch-40-DWV-Plain-End-Pipe-531111/100135041

1 - 25' Discharge Hose
http://www.homedepot.com/p/Watts-2-in-I-D-x-25-ft-PVC-Discharge-Hose-HSCDV25/204407903

1 - 1 1/2" to 3" Reducer
http://www.homedepot.com/p/NIBCO-3-in-x-1-1-2-in-PVC-DWV-Reducing-Coupling-C4801HD3112/100343439

Assorted air fittings to make it compatible with your air compressor.

Here is some background on the theory:
http://en.wikipedia.org/wiki/Airlift_(dredging_device)

Here is a decent layout although I recommend trying to get the supply line as close to the bottom as possible without just blowing bubbles out the end like a bubble gun. Can always put it up 1.5'-2' and just nip off sections of pipe till you think you're good.
http://www.mindspring.com/~divegeek/airlift.htm

Any questions do not hesitate to ask.

Have a good day.

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Reason you use 1 1/2" PVC and 2" ID discharge hose is due to wall thickness of schedule 40 putting the pipe at about 1.90" O.D. simple hose clamp to secure the two together and so you can break it down set it up easier for transport.

The assorted fittings are situation dependent to adapt to your personal compressors or rentals. If you are going to use it while diving scuba or something similar please be safe and use a 1/4 turn ball valve near the inlet point so you can shut it down if it tries to get away from you and doesn't bring you up uncontrollably.

Can always use different sized reducers like a 1 1/2-4" etc or maybe even some sort of roof flashing for around pipes to create a vacuum cleaner type attachment point on the "Business end".


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This might help to get the plumbing from the compressor into the PVC securely and get the air going the right direction too.

Long Bend Wye/Tee
http://www.homedepot.com/p/NIBCO-1-1-2-i...HD112/100345167
(Also the long bend might make a nifty handle for underwater use.)

Adapter to step it down to 1/2" threads. Inserted into a T of some sort.
http://www.homedepot.com/p/Charlotte-Pip...050HD/203811535

I was thinking about the double 90's that we commonly use on our larger airlifts and how far into the pipe that would stick and restrict the pipe, not to mention it would be almost impossible to make such a connection. So I would look into the long bend T and the adapter's I linked only raises the price a little like $5 or so, you can just use a standard T and a reducer bushing as well.


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I'm frozen over at the moment.......

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You thaw out yet? Just coming back to the forums after a absence. Was curious if you ever got to try out the "mini-airlift" I was trying to help design for you. Hope all is well at your pond. I'm dealing with a brown water issue from tearing up my back road during my guest house renovation.


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Was just curious if you ever did try that dredge/airlift thing we had talked about last year.

I have currently made two different drag systems to get an excessive amount of weeds out of the ponds. The previous owners never did anything so now there is a lot of muck/mainly decayed plant matter...it kind of looks like hay. Anyways and then a 1 foot thick floating mass of weeds. Might make another drag too one that is easier to handle. If its not raining all day tomorrow I will try and get some pictures.


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Sorry, I just made it back after a frozen winter. I did not try the airlift system or attempt to build one after all. My wife and I decided to downsize our property (26 acres) to something a bit more manageable and something we can lock and leave while we vacation for extended periods. So, basically, I'm passing the muck on to the next owner and I'm going to let him deal with it.


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