Trash pump (and well) advice please?

I've seen both centrifugal and diaphragm pumps described as 'trash pumps'. I'm not sure if either is appropriate in my case. Here's the
situation - perhaps those with experience/expertise could advise/suggest.
I had a well dug last summer on our place on Texada Island. The area it's in is almost pure sand, and naturally the excavation was caving in and widening as the digging proceeded. At about 12 ft. down we hit an obvious spring, and the excavator operator decided it would be difficult and pointless to go any deeper. Now, at this point he should have perhaps dumped in a bucket of rock before placing the plastic casing, but he was anxious about the hole filling in, and didn't take the time. After placing the casing he did surround it with lots of rock, and we put a plastic ground water barrier around it a few feet from the top (He'd never heard of bentonite).
The water is good, the recovery rate is not bad but not nearly as good as I would have expected given the size of the flow we hit. Sticking a 10 ft 2x4 down the well I discovered that apparently several feet of sand has migrated into the bottom of the well, so that its effective depth is more like 8 feet than 12.
I'm thinking of pumping out the entire well, including the several feet of sand in the bottom. While I"m at it, I'd go down there and drill some holes in the sides of the plastic casing. Of course this should have been done before the thing was put in. Right now water can only enter via the bottom, and must perc through all that sand.
So my questions are:
1) What type of pump is best used to pump (submerged, quick) sand? I expect there to be no rocks, sticks, etc, just sand. 2) Is the well liable to just fill back in quickly anyway? 3) If I do get it pumped out, would dumping a couple of feet of rock into the casing help prevent sand entry, or would the sand just fill in between the rocks and then be even harder to remove than just sand?
There's a Chinese importer here in B.C. who sells what appears to be a Honda clone centrifugal Trash Pump on eBay, for a fraction of the cost of the Honda. Other than the usual comments on Chinese machinery, anyone have any personal experience with these things or this guy?
Thanks in advance to all.
Mickey
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One odd way to do this would be to use a shop vac, perhaps connected to a metal pipe. The metal pipe could break up packed sand. The trick to doing this is not to bury the end of the pipe in the water, but use a steady high speed airflow to transport the sand/water mixture up to the vac. This way you can lift water higher than would otherwise be possible. Of course, the shop vac might not be able to keep up with the water inflow, especially if you have to stop and dump it every minute or two.
For sand, either a centrifugal or diaphragm pump should work, but look for the "suction lift". I assume that the pump would be located above ground.
I would not dump rock into the casing, too hard to get out. Better to develop a system that makes maintenance easy.
What was apparently not used in your case was porous cloth to keep the sand from infiltrating, but I don't know exactly how this could be done in a practical manner, even if you started from scratch. Maybe use a pipe with many holes wrapped in multiple layers of cloth.
Interesting problem.
Richard
Mickey Feldman wrote:

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At one point I had this idea of extending the depth of the well by lowering an interior sleeve into it as I dug down. Probably way too much work to be practical, but it could include landscape cloth.
The shop vac could probably keep up with the inflow, but I can't see pumping 500 gallons with the one I've got!
Thanks for your thoughts!
Mickey
On Sat, 30 Dec 2006 18:48:01 GMT, Richard Ferguson

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Mickey, go talk to the Hydro crew in Powell River and ask to borrow a bar and spoon, by the time you fool around with a pump you can dig most of it out especially if you can drop the water level. If you insist on pumping use a diaphragm pump you will kill an impeller pump with the sand. If you go down into the well make sure you blow lots of fresh air , more than one poor soul hasn't come back out of a well on his own. If you have sand you must be around Gillies Bay.
Best of Luck
Pete

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Yes, near Gillies Bay (Leaper Rd. to be precise). What's your connection to Texada?
I don't know what a 'bar & spoon ' is - new term to me. Google tells me that "A bar spoon holds about 5 milliliters of liquid". Boy, that'll take me a while! If I recall I calculated about 60 gallons per foot of depth, so I've got about 500 gallons to empty to get down to the sand.
Thanks for the thoughts on the fresh air issues. Usually one hears about this with situation where some non-breathable heavier than air gas can get into the enclosed space. I suppose an open-at-the-top-only well is just as problematic.
I did wonder about the abrasive quality of the sand - part of why I posted the questions. Thanks!
Mickey
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mickey_NO_NO_NO@_SPAMinnerimagery.com says...

I assume he means the "large scoops" in the middle of this page...
http://www.mcmaster.com/ctlg/DisplCtlgPage.asp?ReqTypTALOG&CtlgPgNbr61
I cleaned more catch basins than I care to remember with one on my college summer job, but it beats working down in the hole. It'll work under water (though not quite as efficiently) so you may not need to pump out the casing.
Ned Simmons
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Well, there's 8 ft of water above the sand, and up to four feet of sand to remove below that, so I'd think I would do some pumping! Looks like a useful tool for certain jobs for sure...
Mickey
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This is the Bar and spoon I was referring to ( http://www.peaveymfg.com/poleline.html#spoon ). I dug a lot of holes and set a lot of Hydro poles around Powell River and Texada in the early 70's. I left the Sunshine Coast in 1977 and returned 2005 to replace the submarine cables from the mainland to Texada prior to retiring in the spring of 2006. I was an active member of the flying club in those days and knew the small strips around the coast intimately , you had a great strip on Texada that was owned by the Iron mine. Lots of fond memories for the area & people and lots of hair raising stories.
Best of the new year,
Pete

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I think the "Texada Airport", which now has twice a day flights to Vancover (KD Airlines), is probably that strip. It is just north of the village of Gillies bay, and not far from the no longer active "Iron Mine Rd." About a mile or less from our place. I still have one foot in Victoria, but hope to get it unstuck by this spring.
Mickey
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Mickey, how much airflow does your compressor have?
A simple device - often used for underwater excavation - consists of a piece of tubing with a compressed air line attached to a nozzle pointing upwards and a valve.
Your casing can serve as the tubing and a length of 1/4" ID pipe ending in a pair of elbows can serve as the airline and be fitted with a valve and QD fitting at the surface.
If nothing else, renting a trailer-mounted IR compressor for a day would provide you with far more air than you'd need.
This device functions as a pressurized syphon and can lift not only sand but almost anything that can fit inside the tubing.
By using a long-enough airpipe, you could deepen the well beyond the original depth.
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Similar device using a water jet is called an eductor . Quite likely the best bet in this case , the pump never sees any grit . http://en.wikipedia.org/wiki/Water_eductor
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Yes, this may be the ticket. I already have a spare jet pump. I think I've even seen designs for these things somewhere, just didn't think of it for this problem.
Thanks!
Mickey
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The well drillers don't even bother with any attachements. They just lower a pipe hooked to a 120cfm engine driven compressor and turn on the valve. Stand back, it blows water all over! You can use a smaller compressor, it should work fairly well in the confines of the 4" pipe to clean out the sand.
A centrifical pump will abrade rapidly if you try to pump sandy water. The vanes will just disappear, most of the cheaper ones have either aluminum or composite casings so you might go through the case before the vanes go. Not good either way.
You need some sort of sand filter on your inlet pipe. It can be a fine mesh screen or layers of fabric or filter paper. The non woven fabric they use for landscaping weed control is very close to optimum. Drill 1" holes around the bottom 5 feet of a 4", put a cap on the bottom, wrap the fabric around it.
Around here we use 2" driven well points with 120 mesh screen in sandy soil. They run $40 or so,
I think I'd start all over again a few feet away from the first effort and use water jetting to get the pipe in place. Use a post hole auger to get a good start, set up your 4" well pipe with a pair of small pipes strapped along side. Feed water under decent pressure into the small pipes, start tapping the main pipe into place.
RAM wrote:

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Mickey Feldman wrote:

Well, a couple things come to mind.
On the money side of things, hire a Hydro-vac truck. The truck has a large vaccuum pump, a tank, and a long(ish) hose to vaccuum out the trash. $$$ though.
You could homebrew a similar rig using air, as was suggested, or IMO a better bet would be to use a water pump and set it up similar to the dredges used for placer gold mining (google "placer gold dredge) .
You will need to have a place to dump the sand and water, hopefully to be able to let the sand settle out and allow the water back in to be put back to work in removing more detritus from the well.
Once the well is cleared out enough, then pump it clear of water and allow for recovery a couple cycles, to clear the silt that is sure to accumulate in the wellwater.
All in all though, I think the trick is to not be driving the sand through the pump, but to be using the pump to drive the sand through the pipe.
Cheers Trevor Jones
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On Sat, 30 Dec 2006 18:31:13 GMT, Mickey Feldman
...

I'll pass on the pump question, except to say that removing your small quantity of sand _once_ is probably insignificant to the life of any pump. We must have moved that much sand with our expensive deep well pump while testing the first sandy well.
When the drillers tried to rescue their first, improperly packed effort at my recent new well, they chose to dip the sand out. They had a section of pipe with a trick valve at the bottom, which they lowered into the well until the valve trigger hit bottom and water and sand rushed into the pipe. When they lifted it back out, the valve captured the mix. They used this in preference to the normal mechanism of blowing compressed air up from the bottom of the casing, because it supposedly wouldn't draw as much more new sand toward the well.
2... Yes. They tried various finely slotted casings and wire wrapped filters, but the finer sand kept getting through.
3... What works, perfectly, is the proper special mix of graded packing sand. I don't know where they got it, but apparently drillers know. It is a special mix of the proper proportions of different sizes of graded sand, designed to fit together in a pattern that is impervious to newly arriving sand, no matter how fine it is. Since my casing was slotted over about 80' of length, there was no way to retrofit it - they had to drill a new well, and pack it with the magic sand like they should have the first one.
I wonder if you could just cover the bottom of your well (after removing the present sand) with a layer of graded packing sand. You might have to restrain the top surface of the layer with some kind of screen, and then maybe your layer of rocks. The screen only needs to be fine enough to restrain the largest grade of the sand - the rest will pile up behind the larger sizes. In my deep well application, the hole is 8" and the casing 5", so there is only a 1.5" layer of magic sand doing the trick.
Loren
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Loren Amelang wrote:

I'm pretty certain that the OP is describing a shallow well with a 4 foot or so diameter casing. Deep well, casing related tricks prolly won't work too well there.
I had a similar setup while I was living on Vancouver Island, 16 feet deep, 4 foot diameter casings. My neighbor was on a 10 foot deep hand dug well.
Cheers Trevor Jones
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In which case, an air pipe and a section of 4" plastic pipe will work well.
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Yes, this is a 3 ft diameter dug, not drilled or driven, well. However, the info about magic sand is interesting and might be part of the final solution. Thanks!
Mickey
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On Sat, 30 Dec 2006 18:31:13 GMT, Mickey Feldman

Most centrifical trash pumps are gonna have a hell of a time sucking up a 12 foot head of water unless you can prime it really well.
You on the other hand, can back wash or bail out 2 feet of sand easily. Then run in a sand point with your pump.
Geeze...12 feet..you can hammer a well in that deep using 2" pipe and a block and tackle, or simply hose your way down with your trash pump hooked to a joint of 6" pvc and an adapter. Put in sand screens and a liner. Yall didnt put a cap on the end of the casing before you set it?
Well..12 feet..move over a foot and water drill a new and proper one.
Gunner, who lives where 400 foot wells are common. Political Correctness
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
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Mickey Feldman wrote:

Diaphragm type pump. Sand will eat a centrifugal pump up rather quick.
The problem is that the sand will start to compact as you extract the water unless you can keep it stirred up. I would probably pump down the water using a home made drill point to get below the sand. Then use a dipper bucket to hoist the sand out.
IF the sand is coming up through the open end of the pipe and that is the only place then you could dig below the pipe and create a pocket. Then drop in some pea gravel at the bottom and some filter cloth in a couple layers with some more pea gravel to hold it secure.
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