#7 Slot Sand Pt. vs. Casing vs. Wound wire?

[bcd11]

I am driving wells in VERY FINE sand for a lawn watering system. I jetted/drove a 4' x 1 1/4" #10 slot PVC sand point to a depth of 24', my water level is 15'. After 4-5 hours of operation my sand point has filled with
2' of sand. I am using a centrifugal pump and getting 27 gpm at 40 psi from two 1 1/4" wells.

I would appreciate opinions on using a #7 Slot sand point instead of #10, not using points and driving casings to a depth of 25'-30' into which I would lower suction pipes w/strainer and foot valve, or using wound wire points.

I'm leaning toward the casings which would be flushed out and the suction pipes then lowered into. I think this is what Bob NH meant, but I'm not sure, when he suggested 4" or 6" casings in an earlier post. It seems to me if I keep the end of the suction pipe far enough above the bottom of the casing I should avoid filling the system with sand.

Any thoughts from someone that has tangled with VERY FINE sand would be most appreciated or if Bob NH reads this post maybe he could confirm my slant on his earlier reply.

Also, can someone tell me how a #7 slot compares with 60 mesh gauze from a size of opening standpoint? I have a metal point with 60 mesh gauze that doesn't seem to be filling with sand. Even though it seems to be working I am hesitant to drive another metal point w/drive pipe as I had to pull one earlier and lost the point.

Thanks in advance for any thoughts and suggestions.

Bart

 

[Speedbump]

If your getting that much water, your point shouldn't be filling with sand. If your not getting any sand up top, don't worry about the sand in the screen.

A ten slot is the same as a 60 gauze. The seven is three thousands of an inch smaller opening than the 10 slot. It will give less water than the 10 slot, but if you are pumping sand, that would be the one to try.

Leaving a casing open at the bottom in sand ends up with several feet of sand up into the pipe which shuts off the water supply.

bob...

 

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[bcd11]

Thanks Speedbump

Bob,

Thanks for the QUICK reply.

I'll run another flow test and make sure the 27 gpm is still accurate.

Good idea on not getting sand at the top. I can easily get insde the pump and look for sand. The oscillating sprinklers seem to be sand free.

IF the point continues to fill with sand what is your opinion about driving 4" or 6" casings to a depth of 24'-25' and lowering the suction lines into the casings and forgetting about drive points?

Again Bob, I really appreciate you taking the time to reply.

Thank you,
Bart

 

[Speedbump]

Bart, you can't just drive casing into the ground, clean it out and expect it to stay open. That's what the screens are for. When drilling a small well like yours, the casing is driven first (sometimes a piece at a time while cleaning each one out) then the point is put in last. It is small enough to fit through the casing so it can be driven out the end of the pipe into the saturated sand to allow water into the casing. If you drove the casing and then cleaned it out to the very bottom; you would not get any water out, because as soon as you put a vacuum on the casing, the water along with a lot of sand would immediately shoot up the casing shutting everything else off permanently.

bob...

 

[bcd11]

Bob,

Again, thanks for the fast reply and your PATIENCE.

After reading your reply and looking at the pump manual (for the umteenth time) I'm not sure I correctly described my plan of attack.

 

[Speedbump]

Location: Long Beach, IN-Near Lake Michigan shoreline

Isn't Long Beach in California? Where are you near Lake Michigan? Which side, Michigan, Wisconsin, Indiana or Illinois?

bob...

 

[bcd11]

Bob,

Again, thanks for the fast reply and your PATIENCE.

After reading your reply and looking at the pump manual (for the umteenth time) I'm not sure I correctly described my plan of attack.

What I meant to say is drive a casing (4" or 6") to a depth of 24'-25', about 10' below the standing water level. I would flush/suck the sand out of the casing. Then I would lower a 1 1/4" or 1 1/2" suction pipe, with screen/strainer and foot valve on the bottom of the this suction pipe, to a level of 20' leaving about 5' of water under the foot valve and about 5' of water above the bottom of the suction pipe.

I hope this better describes what I'm pondering, it is what's shown as a cased/ dug well in the pump manual. If you think this would still result in drawing sand into the system I'll scratch this idea.

Thanks Bob.

Bart

 

[bcd11]

LOL!!

Long Beach, IN is not QUITE as well known as Long Beach, CA.

We are about 30 miles across Lake Michigan from Chicago. On most any day we can go to the beach and see the buildings in Chicago. On a clear night it's quite a sight to see the buildings lit up and the planes arriving and departing the Chicago airports.

As I think about it, it's kind of funny to think of all the fresh water in Lake Michigan that is about 300 yards from my house and I'm having quite the go on getting water (minus the talcum powder grade sand) from 15' underground. Seems as though the train is headed out of the station in the wrong direction. Although if you were to talk to my wife, she doesn't really mind my pre-occupation with the wells. Her take on it is if I wasn't thrashing around out in woods driving wells all over the place I'd be closer to, or God forbid IN) the house getting into who knows what kind of trouble with other projects.

Bart

 

[Speedbump]

Now I know where you are. Not that it helps. I'm not familiar with that part of the Lake.

I would flush/suck the sand out of the casing.

That will only work as long as you keep a good head of water in the pipe. Lower your pipe and screen/footvalve, hook up the Pump, fire it up and watch the water level go down as the sand comes right back up into the pipe. You can have as much as a 10 foot plug in the bottom. This sand will then settle down and act like a valve between the aquifer and the Pump. Now, if you can knoch a smaller screen out the bottom leaving a short piece of pipe up in the casing sealed to the casing, you might have something.

bob...

 

[bcd11]

...as much as a 10' plug in the bottom.

Thanks for THAT warning! Me thinks after leaving a two week old $60 well point in the ground, taking a week to pry 15' of metal pipe out of the ground, and having 2' of sand in the bottom of my 4' sand point I'll pass on the potential 10' plug in the bottom of a half-baked idea. I'm fast coming to the conclusion even if it's half broke don't fix it.

This morning while we were exchanging e-notes I was furiously watering away, figuring I'll get in one last GOOD lick before I completely seal the last 2' of one of my points. After watering for nearly three hours I ran a tape measurer down the suction pipe and the sand had not filled in anymore of the point. That was a head scratcher!

Try this on for size. Is it possible I drove the point 2' beyond the bottom of my water vein? Could it be that as the water entered the point through the 2' of slots still in the water bearing sand the incoming sand was dumped in the bottom of the point because no water was entering the bottom half of the point? When the sand filled the point to a level that matched the lower boundry of the water vein the sand no longer stayed in the point but was carried up the suction pipe? When the pump is turned off and some of the water drains back down the suction pipe any additional sand is then forced out of the point down to the level of the bottom side of the water vein?

Anyhoo...right now I'm getting 28+ gpm from two 1 1/4" wells, appearing not to be getting anymore sand in my sand point, and able to water my lawn. My common sense tells me NOT TO MESS WITH IT... and occasionally measure the sand in the bottom of the sand point. I would like to raise the sand point about 2' and see if the sand clears out. However, after the week of fun getting one metal pipe out of the ground, sans point, there's this voice in the back of my head saying, "Don't be an idiot for only 2' stuck on the end of a PVC pipe."

I'm thinking about driving a third well because the pump is rated for 44 gpm at a depth of 15' and I'm getting 28 gpm; at least it should be close to the rating. After your possible 10' plug warning I'll probably just drive a casing to the water level and then drive my PVC point and suction another 7'. If and when I have to figure out how to pull the point without breaking the pipe it should be easier to get it out of 7' of water bearing sand and an empty casing than 22' of wet/dry sand.

I'm having trouble finding a #7 slot sand point on the internet. Do you know of a supplier I could contact?

Once again Bob, thank you for all of your time, advice, and patience. You have no idea how much your comments have helped.

Bart

 

[Speedbump]

Your getting good at this. Your assessment of the 2' of sand in the bottom of your point sounds like an exact re-enactment of what happened.

The 28 gallons per minute is a lot of water from two 1-1/4" wells. You should be proud.

I do have a 7 slot Stainless Steel Screen that you can have for $50.00 plus freight. I inherited it from my Dad when he quit drilling and still have a dozen or so more of them in different slot sizes. You won't get as much water with the 7 as you will with a 10 or a 12 slot, but it will produce water.

bob...