Replacing Well Point


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Old 07-05-12, 04:14 PM
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Replacing Well Point

I've got to replace the point in my 50 year old shallow dug well.

The well is 17 feet deep, and the water in it varies in depth from 5 feet down to a couple of inches, depending on the water table. The soil is sand. About 15 years ago I dug a 6 foot deep hole at the bottom, and put a point down there surrounded by gravel. That point is now pretty well clogged and I'd like to replace it this summer.

General info... There's a 1/2 hp single drop jet pump and 40 gallon pressure tank in the basement for the well. I ran new 1 1/4" plastic pipe to the well 15 years ago that connects to a check valve then about ten feet of galvanized pipe, then the buried point. Everything still works, but the point is so clogged it's like sucking water through a pinched straw. The water is acidic and has a lot of iron. I run it through reverse osmosis for drinking.

Basic questions... can I replace the galvanized pipe with sch 40 pvc? What kind of points are available and what should I use, given all the iron in the water, the sandy soil and all the new gravel that will be placed around the point? The old point has a fine mesh screen that keeps the sand out but seems to clog with iron pretty easily. Could I go with a coarse screen at the point to keep gravel out, and a cleanable/ replaceable screen or filter after or before the pump to catch the sand? I have a sediment filter after the tank, but there's never any sand in it, just iron.

Where should the check valve go? I don't like the idea of putting it down the well since it's so difficult to service anything down there. Would the check valve work OK at the pump if I added a valve to facilitate priming? Can the check valve be horizontal? Will sand affect the check valve?

One advantage to putting the check valve by the pump is that I could easily pump high pressure air or water down the well to help unclog the point when it gets fouled. If I'd installed an easy way of blowing out the point I put in 15 years ago I might still be getting a lot of water from it.

What I'd like to do is fix this so I never have to go down the well again. I'd like to be able to do all future maintenance in the basement near the pump.

Anyway, I'm looking for some advice from more experienced folks before undertaking this task.

Thanks.
 
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Old 07-06-12, 07:41 AM
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To answer all your questions, the comment would read like a book.
You might want to read this page first:
Water Well Helpline

You will find many answers to your questions starting about halfway down.
Look at the picture of an irrigation well and pump. It should look familiar.
 
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Old 07-07-12, 06:46 AM
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Thank you for the link. There is a lot of useful information there.

I guess the main decision I face is what type of point to bury in gravel at the bottom of the well. The points used in the past have been drivepoints for sandy soil. They keep the sand out, alright.

But they quickly foul, and I don't need a drivepoint. A coarser screen might not foul, but would let in sand. I could see a section of 2" pvc with many small holes drilled in it making a good "point", but then sand will come up.

If I use a point that permits sand to pass through, is there a good way of dealing with the sand at ground level, either before or after the jet pump? Or is it necessary to keep the sand out at the point?
 
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Old 07-07-12, 07:35 AM
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If the the sand is so fine, then flow will be limited. The object is to have the point in gravel or course sand. Fine sand is round and is called "beach" sand because it was rolled around on a ancient beach. "Bar" or builders sand is also called "square" sand. The reason is that it was originally further out from the beach where it didn't get rolled around as much.

So what is supposed to happen is that the square sand is supposed to rearrange itself and because it is square it will "build" itself up with holes to let the water through. It's kind of like building a concrete block wall, but with spaces between the blocks. Under the right circumstances, a pea gravel filling should even be necessary.

That's the theory, okay? Reality is different as you know. So you have it right. You have three choices: Go deeper and hope you find courser sand, put in a finer point (they are around, but not at the Big Box stores) but you know it will jam, or use a spin down filter.

Actually there is a 4th, but it may not help you. Even though you have 4 feet of screen, many wells only have one foot where water is flowing through. So "stacking" the points can help if at least ~14 feet of standing water is in the well.

There are advantages and disadvantages to all of them. Let's just say you have a courser filter and use a spin down filter. That will work for a while, but every time the pump turns off, what ever sand is in the water will fall to the bottom of the inside of the point. Hopefully that sand will get stirred up because if it doesn't, you can fill the point up.

Now, what you might want to do, rather than pull the point all the time is to backwash it more. That's called "Well Development" and air is a good choice.
I have a couple more links for you:
http://www.campbellmfg.com/brady/doc...stallation.pdf
Section 10: Well Development
Well Development
 
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Old 07-07-12, 10:10 AM
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I had originally planned to blow out the point with air, but I can't get the check valve off the 1 1/4" galvanized pipe. The threads are corroded after being down the well for 15+ years.

I can cut the galvanized pipe, but then I'd have to cut new threads on it, right? I don't have the equipment to do that.

Anyway, I like the idea of a coarser screen and a spin filter. They don't look too expensive. Would the spin filter go before or after the 1/2 hp jet pump?

By stacking, do you mean multiple points ? That is an idea worth considering.

Going deeper is not an option. Go a bit deeper around here and the water starts smelling like sulfur.
 
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Old 07-07-12, 06:14 PM
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The spin filter goes after the pump. Stacking is covered in the Brady booklet. There is a lot in that Brady booklet. It is rather dense, so speed reading while day dreaming about something else is NOT the way to read it. Don't skip past the things you think you know in there. You might want to put in another shallow well and link them together. The trade calls that a "well field."

I have a pipe threading kit. It's not as high tech as the pros use, but it was cheap. I got it at Harbor Freight -- it's cheap, but it works like a champ with cutting fluid. There are places around here that charge a dollar a thread. They got electric pipe threaders so it's no big deal for them. I got the kit because I got tired of driving and paying a couple of bucks every time I needed a pipe thread.
 
 

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