New to wells and to this forum

[Mauro]

Hello everyone

I’m new here and new to wells too, just successfully dug a 4.6mt bore hole for a submergible pump with compressed air and water having found very shallow water table.

However, no matter how deep I go, after 3.6mt all I get is sand.

I got the pipe deeper by 1 more meter (4.6) but the hole fills up with sand again up to that level living me with a 3.6mt deep well containing 1.7 mt head of clear water.

My question is, do I have to put a cap at the bottom and just be done with 3.6 mt or shall I push it to 4.6 and fill that 1mt with gravel?

By not having the cap I can use a smaller pipe to blow the sand away, at least for the most part, and trow gravel in instead stopping at 3.6.

Of course I would use pea shingle also around the bore above the water level to discourage sand from entering the well.



I appreciate the knowledge of some of you more experienced.

Many thanks.



Regards

 

[Valveman]

The holes or slots need to be small enough to keep the sand and gravel out. Look at using a sand point.

 

[Sponsor]

 

[Mauro]

The holes or slots need to be small enough to keep the sand and gravel out. Look at using a sand point.

Thanks, I'm aware of the slots size, my question is about cap or gravel at the bottom of the well ?

 

[Reach4]

Thanks, I'm aware of the slots size, my question is about cap or gravel at the bottom of the well ?

You did not mention having a casing with slots/screen standing by.

The gravel (pea shingle?) around the slots would be just big enough to not fit through the slots. Pea gravel would be too course to stop sand.

 

[Mauro]

You did not mention having a casing with slots/screen standing by.

The gravel (pea shingle?) around the slots would be just big enough to not fit through the slots. Pea gravel would be too course to stop sand.

Sorry, I thought the slot were implicit or how would the water get in . .
Thanks for that, I shall obtain some finer gravel, however I'm still puzzled by the cap at the end of the bore, if I use one I loose 1 mt of depth (which is filled with sand anyway) but that could be gravel . . So . . cap yes ? Cap no ? ____ this is the main question.
Once again thank you

BTW, this well is not for drinking water but just for general outdoor purposes.

 

[Valveman]

Usually the bottom of the casing is shoved down into the clay, so there is no need for a bottom cap. But if there is no solid bottom to land on, the cap will keep the gravel from coming underneath. However, it is hard not to pop a cap off if you hit the bottom with the pump or a sand bailer.

 

[Mauro]

Usually the bottom of the casing is shoved down into the clay, so there is no need for a bottom cap. But if there is no solid bottom to land on, the cap will keep the gravel from coming underneath. However, it is hard not to pop a cap off if you hit the bottom with the pump or a sand bailer.

Thank you for your input, it makes sense, perhaps the only reason why I was thinking of capping it at the bottom end is that, since the pipe fills up with sand up to the same level no matter what I do, perhaps with the cap I could make use of that extra meter of pipe as water reservoir to avoid accidental pump cavitation . . however, if the sand eventually was to make its way through from above (which I think it would) slowly but surely it would sediment inside and the extra 1 mt pocket would slowly reduce itself to nothing. It is also true though, that this system could be serviceable every now and then by pumping fresh water and compressed air down in order to remove the sand and restore the extra depth of the pocket. Any thoughts about that ?

 

[Reach4]

It is also true though, that this system could be serviceable every now and then by pumping fresh water and compressed air down in order to remove the sand and restore the extra depth of the pocket. Any thoughts about that ?

If the static level is high enough, an air lift pump would be the good tool to lift sand from a well economically. You want the water below the water level to be more than the distance from the water level to the output.

https://terrylove.com/forums/index....please-borehole-supply-in-the-uk.61806/page-2 talks about an air lift pump for a deeper well.

An engine-driven high cfm compressor can blow sand out, in a geyser, quickly. Those are expensive to rent, but maybe you have the use of one.

 

[Valveman]

You could push a sand point with a fine screen down the well and draw water with a jet pump.

 

[Mauro]

If the static level is high enough, an air lift pump would be the good tool to lift sand from a well economically. You want the water below the water level to be more than the distance from the water level to the output.

https://terrylove.com/forums/index....please-borehole-supply-in-the-uk.61806/page-2 talks about an air lift pump for a deeper well.

An engine-driven high cfm compressor can blow sand out, in a geyser, quickly. Those are expensive to rent, but maybe you have the use of one.

Forgot to paste the link . . this is how I did it as an amateur

As you can see I have no problems at all removing sand from the lower part of the pipe but after an hour or two the sand comes back to the previous level, more precisely it fills the lowest part of the 100 mm pipe for about 1 m. To sum up I have a 4.5 m pipe berried in sand for the last 1 m, 1.4 m of water and 2 m to the output level.

[QUOTE=You want the water below the water level to be more than the distance from the water level to the output.
Not sure if by "the output" if you mean the top of the well were water will be extracted from, if so I don't satisfy the requested ratio since I have 1.4 m of water and 2 m to the top of the well. However, digging further does not seem to produce a deeper water pocket as it always fills up with sand back to the same point, or shall I try ?

 

[Valveman]

Again, the screen or perforations on your casing must be small enough to keep the sand out. Sand makes a good filter to keep other sand out, but you have to have the right size screen. See how a sand point works.

 

[Reach4]

Not sure if by "the output" if you mean the top of the well were water will be extracted from, if so I don't satisfy the requested ratio since I have 1.4 m of water and 2 m to the top of the well.

I meant the point where the flow goes horizontal, which is at least as high as the top of the well.

From https://www.sciencedirect.com/science/article/abs/pii/S0920410513002350

So it is not a hard limit. You would have a submergence level of about (1.4/3.4)= 0.41 or less. But an air lift pump lifting sand would seem to have a harder time than one that lifts only water.

https://www.researchgate.net/publication/328631507_Experimental_Study_of_Air_Lift_Pump_Delivery_Rate does discussing pumping sand with water. It is a very hard read, and I won't be attempting it.

 

[Mauro]

I meant the point where the flow goes horizontal, which is at least as high as the top of the well.

From https://www.sciencedirect.com/science/article/abs/pii/S0920410513002350

So it is not a hard limit. You would have a submergence level of about (1.4/3.4)= 0.41 or less. But an air lift pump lifting sand would seem to have a harder time than one that lifts only water.

https://www.researchgate.net/publication/328631507_Experimental_Study_of_Air_Lift_Pump_Delivery_Rate does discussing pumping sand with water. It is a very hard read, and I won't be attempting it.

All very interesting, thank you so much for the links, I am reading now.