"Wrong way" suction in well pipe

[ChiefEngineer]

I have had a low-yield well for a number of years. After failing to get anyone to
blow it out I did my best: bought 300ft of pex and attached a nozzle and my air compressor.
Here is what happens: with the pump ON I jack up the air pressure down there to 200PSI
and feel the outlet pipe opening: it is sucking air IN. I cover the opening briefly which appears to prime the pump.
I uncover it and the suction REVERSES and start to blow out nasty water for quite awhile, until
the air pressure dies back down. Rinse and repeat. Any guesses? I am thinking theres a hole in the polypipe
that stops it priming, and the air pressure takes the place of water temporarily priming it.

 

[Reach4]

Is the 300 ft of PEX all above ground, or is it going down the well?

What is "the outlet pipe"?

what is the "nozzle" pressurizing? Are you putting air thru a port in the well seal to pressurize the casing, or what?

Is your pump above ground? If so, how many pipes connect between the pump and the well?

 

[Sponsor]

 

[Bannerman]

Assuming you are referring to a submersible pump, it should be fully submerged in water and so will not require priming.

To clarify, where are you inserting the 300' of ? diameter PEX line, within the well casing, or within the drop pipe (outlet pipe) from the pump?

Is the 'nozzle' end of the 300' of PEX submerged in the water below the pump, or is the pump located below the nozzle?

What is your well's total drilled depth, its static water level, and how deep is the pump placed within the well?

Describe your air compressor' CFM capability and tank capacity. Does any water blast out from the well casing when the 200 psi compressed air is initially released into the well?

To blow out a well, usually requires a tow behind, engine driven compressor to supply the high volume of air at sufficient velocity and duration to propel the water from the bottom of the well, out through the top of the casing, similar in appearance to a gieser.

If you supply compressed air into the well with the pump shut off, does a vacuum continue to be created within the outlet pipe?

 

[Fitter30]

Was the well casing sealed around the 300' pex? Only way that drop pipe could be sucking air is by a venturi effect. Àir pressure drops off instead moving air across the drop pipe then it gets pressurized. Well 200' deep 86.5' to water to the top put another 30/lbs 69' of height. Have no idea what 200lbs would do to the structure.

 

[ChiefEngineer]

Wow, great questions! Here is what I "perceive" is the detail (I guess at much of this): well is 140ft deep with water at 100ft. Pump is at 120ft stuck in place by either sand or warping, but a big pull only stretches the polypipe---have not pulled the wire yet because the pump still is still working. The 300ft roll of pex from Lowes ($94) has about 108ft of it down the 4 inch casing, where it hits something and won't go further...that something may be sand...there is a lot of backpressure when I turn on the air. The "nozzle" is a pex-connected fine attachment you might use on an airgun for blowing out a filter or motor. The other end of the pex above ground is attached to a 200psi shop oiless compressor that can do about 6CFM at 90psi (I need something bigger but a truck can't get near this...so I may buy another and daisy-chain them with a manifold). The way I have had to snake the pex down there next to the polypipe makes the seal imperfectly tight, and yes, some of this air passes in the casing. The pipe that is coming out of the casing that I am covering/uncovering is an garden-hose-sized attachment I direct into large containers. When the water/sand/air starts to come out it chokes/pukes it up...no continuous flow....a "controlled-little-geyser". I am trying this because it is in a wellhouse full of gear/totes/pumps/tanks/pipes that have been making this low yield well viable, and with a 3/4HP submersible stuck down there but working, the jetting process employs the pump itself with the water that is already down there...I am just injecting air with it trying to clean without doing something destructive, and the mystery to me is how hot air from the compressor is getting pulled through the pump (or a crack in the polypipe(?)) and initially vaccuming air from the above ground outlet pipe. When I seal this pipe (hose-end) hard, the pressure actually reverses in about 20 seconds and the geyser cycle starts...then I eventually run out of high-psi air and it starts blowing air without water. Since this is not a tradtional jetting approach--in fact one of the reasons is to potentially unstick this pump without killing it or the casing-- the only solution I am foreseeing is increasing the pressure to see what it can bear. Hope this makes more sense.

 

[Valveman]

90 PSI should be plenty. But I would a compressor that would put out maybe 50 CFM and have no nozzle on the end of 3/4 pipe. You are going to need a compressor and pipe large enough to blow it out or it will just settle and pack down even worse.

 

[Bannerman]

the mystery to me is how hot air from the compressor is getting pulled through the pump

The hot air is not from the compressor, but will be from the well pump's motor. Since there is so little-no water exiting the drop pipe, there will be insufficient water flowing past the motor to provide cooling. This situation will be further compounded if the pump is actually partially buried in sand/silt.

Perhaps your pump is actually overheating, and is being periodically shut down temporarily by an internal thermal switch within the motor. Suggest obtaining a clamp on amp meter to monitor for an extended period, the amps drawn by the pump when there is 0 flow, and also while water, sand, silt etc is being blasted out for the short duration.

For there to be a vacuum at the top of the drop pipe, signifies the water level falling lower within the drop pipe. This would occur if there is a hole in the drop pipe or, if pump's internal check valve is stuck open, particularly while the pump is shut down or if the pump is running but while there is insufficient water entering the pump, which would likely result in cavitation at the impeller.

I suspect in your situation, the compressed air supplied above the pump, is pushing some volume of water up the casing for some distance, which is resulting in a reduction of the water level at the pump. If there is a hole or stuck check valve, then the water level within the drop pipe is likely to drop, resulting in a vacuum above. Once there is insufficient air remaining to keep the water suspended within the casing, then that water is falling back down, so the resulting surge is sufficient to allow the pump to briefly propel water and debris up and out from the drop pipe.

As Valveman stated, to better clear the well will require a much larger volume of air, delivered rapidly and constantly over a sufficient time period to blast the debris directly out from the top of the well casing, not through the pump and drop pipe.

 

[ChiefEngineer]

What I have is 1/2 pex going down there next to a fat 4x wire and 1 inch polypipe. There is not much room in the 4 inch casing. Since this is in a significant building with a raftered hurricane-proof roof I have little hope of joining sections of pipe into it. I am surprised the pex has not doubled back up on itself during the brief periods when I shoot 200psi down there...when it drops to about 30 psi the water stops and it is all air. The hot air being produced by insufficient water cooling can't be detected with the air pressure on: the pump can run all day and no palpable pressure comes out of the well pipe...means to me there is a split in the polypipe somewhere. Additional proof seems to be this: when I tension the polypipe up the performance improves...in other words a vertical crack is getting "sewn up" to some smaller extent. I have measured the pump with a clamp-on and it never exceeds 9A. One would think a thermal overload would kick in but maybe I don't grasp how that works: I can hear the pump run...it never trips a breaker of shuts down, even "dry" as we assume it is...I have been hoping it is churning nasty water down there and not air. What comes out every day is not really getting clearer: it is almost a milk quality of clay/sand/silt . If left to settle overnight the bottom of the bucket is brown and the water is clear. I think I am looking for a way to increase pressure while somehow directing a potential big geyser out some pipe I make a hole in a wall for.

 

[ChiefEngineer]

I suspect in your situation, the compressed air supplied above the pump, is pushing some volume of water up the casing for some distance,

This is some of the best information I had beed hoping for. I get just about enough water to take care of some latrine matters and irrigate my banana trees since it has not rained here in 47 days. I was beginnining to think the water table had dropped. Despite this situation I have a 100+ year old fig tree that is putting on new leaves and fruit...so either it is finding what it needs (it is right next to the well) in the surrounding soils, or it is the reason my pump is mysteriously stuck.

 

[ChiefEngineer]

90 PSI should be plenty. But I would a compressor that would put out maybe 50 CFM and have no nozzle on the end of 3/4 pipe. You are going to need a compressor and pipe large enough to blow it out or it will just settle and pack down even worse.

So I found a compressor I can rent from Sunbelt for a small fortune. Assuming I don't care about geysering inside a building, I could cut a hole in the metal roof, section together schedule 80 PVC, which turns out to be stupidly heavy, rig up some harness to support the weight as I assemble/drop it, then turn on the pressure. Will the result be that the stuck pump itself rocketships out of there? Is that why the people I have had out here all say: "new well"? They cannot get a truck back to the building due to trees and terraine...that is what they claimed.

 

[Reach4]

The pump will not rocket out.

High high is the roof?

 

[ChiefEngineer]

The pump will not rocket out.

High high is the roof?

Fortunately, the "careful planners" who put this in surrounded by a concrete foundation, put it in the corner of the building, not only under the lowest point in the roof (8.5 ft.), but a 2x10 support rafter that prevents cutting a simple hole. Beyond that amazing bit of construction, in an area that doesn't freeze, and an area where a water well has never blown away from a hurricane as far as I know, I am now told when this was built it is HIGHLY LIKELY it was made with no gravel packing as a matter of common practise. Similar to my pool equipment that is so jammed together that when a single valve fails it requires a $10K+ replacement of every single part of the assembly, or my almost new car that started "lighting up" with transmission failure at 70K miles after being parked for a couple days. It just somehow "goes bad", with a similar solution awaiting.

 

[ChiefEngineer]

For posterity's sake I'd like to report that my half-assed engineering solution appears to be paying dividends in the following sense: I stopped getting water altogether; now I get water. Furthermore, with this weird suction/reversal phenomenon I have been tweaking the dials on the compressor and have discovered that after the pump gets primed and the water starts to burp out, there is a "sweet spot" where if I maintain VERY LOW pressure being transferred into the casing it has the beneficial effect of prolonging the water output and the cleaning action. Of course if there is an infinite amount of cleaning things will eventually get a little tedious.

 

[ChiefEngineer]

For anyone still interested some things happened today that got me crapless excited: for the first time in months clean water started to flow on its own with NO air pressure except to assist the priming process at a very low pressure level. After I shut down the well I could not replicate that, except to note: I could "hear water where there was no water" (---a vague Melville turn on words). It would appear somehow, in some way, with the pump on but not producing, water was being forced up the air-pex, possibly above the surface of the well itself. Upon detaching the air hose there was pressure coming out of the supply end, a strong gurgling of water, and repetition, like turning off the air pressure had resulted in siphoning up 100+ feet, or residual air in a pocket beneath still forcing some water up. Whatever is happening had for at least awhile looked like a return to near-normalcy, albeit with a weakened pump/flow, but so much water I had no plan where to put it as my storage units were full...I poured it in to the swimming pool.

I know this is strange but it is a source of great excitement in my life. Perhaps I am stumbling upon some sort of physics-defying jet-pump ram action, like if I were to stick a second pex pipe down there sucking instead of pushing it might really produce water, and leave the stuck pump relegated to de-mucking...all specualtion appreciated.

 

[Reach4]

Here is an idea: Run the water through a low-backpressure filter and then back down the well. Maybe make like a settling tank to take the water and then a gravity drain sending water back down the well. Or a sluicebox like thing.

What I am hoping for is that your filtering is taking out sand/silt, and that serves to help de-mucking. So the big suggestion is to return the water down the well. I don't know if that would demuck better. It would depend on whether your water level was dropping too much. It could be worse than sucking water from below the pump for clearing solids. Just an idea.

Part of your description was hard for me to follow... maybe too poetic/literary for me.

 

[ChiefEngineer]

What I am hoping for is that your filtering is taking out sand/silt, and that serves to help de-mucking. So the big suggestion is to return the water down the well. I don't know if that would demuck better. It would depend on whether your water level was dropping too much.

It is demucking better every day. I've been dreaming of how to deploy that return water scenario. Whatever is in that orange/black muck it's not all sand. By morning a six-gallon bucket that was brown is clear, but there is 1/8 inch of sticky-nasty left on the bottom.

You are right---I am too obscure---I had a professor drill home on me once the CORRECT quote: "Water, water, every where, / Nor any drop to drink". That describes things better around here, since I buy distilled water to drink and cook with. I am surrounded by pipelines and oilwells. I can report sadly that what is coming out of the well is killing the plants I put it on, even banana trees that are the heaviest feeders---they "eat" raw manure that burns other vegetation up.

 

[Reach4]

Ouch on the water. You should get a lab water test, including organics, if you plan to drink the water.

Regarding filtering the muck, if you put a teaspoon or two of muck into a glass or glass jar with water, and stir, how long does the sediment take to settle?

 

[ChiefEngineer]

Thanks for taking an interest in my saga! To answer your question...I'd say it settles in about an hour to a point where it it is never completely clear. Then the slightest disturbance clouds the whole thing again. Yesterday and today, when I went to dredge the well, the first "stuff" out of it was BLACK, and later turned to coarse sand. One more change: the "wrong way suction" ceased, which had resulted in the priming phenomena, so I went back to pumping high pressure air down there, and the system started producing until the unthinkable happened: my new air compressor, not even a month old, "failed"...pressure regulator stopped passing pressure from the tank to the outlet; tank still pressurizes. When I went inside to find how long I had to return this with its gigantic restocking fee, I came back out to a pleasant flood: with NO AIR pressure clear nice water was being being pumped all over the ground. I proceeded to fill every bucket I could find, then started pipingit to my pool, where the flow eventually ceased until I shut off the pump. During this time there was almost no sediment coming out: just nice clear water. There is no telling how long this will go on, or of it will at all...but this experience has cleared up a number of possible bad assumptions.

...and I will NEVER drink this water...I'm just going to assume it's OK but still not drink it, even though I filter it to death before it gets to my house...

 

[ChiefEngineer]

I get incredibly strange behaviour out of this well. Two days ago it seemed "clean" with just some coarse sand then pure-looking water and good flow. The next day the same. Then on the third nothing at all. One of the strangest mysteries I had was a couple years ago I could not pump water into my pool from a hose coming off a wellhouse spigot. That required an increase in height to the outlet of the hose of about 5 feet. But if I laid a 300 foot hose on the ground off that same spigot I could water trees on my property line quite well. It seems like that extra height with the extra atmospheric pressure stops some priming action, either due to age of the pump, or some hole that fails to equalize pressure. Yesterday I had big strong flow, until I ran it "uphill" just a few feet, then it simply died. Like the "head" got too great, perhaps due to failed foot/check valves?

 

[Reach4]

But if I laid a 300 foot hose on the ground off that same spigot I could water trees on my property line quite well. It seems like that extra height with the extra atmospheric pressure stops some priming action, either due to age of the pump, or some hole that fails to equalize pressure. Yesterday I had big strong flow, until I ran it "uphill" just a few feet, then it simply died.

Is "it" the pump? Raising the pump can have a big effect with a suction pump. It is easier to push water than to pull water.

You don't want any part of the pump or suction line to be more than about 25 ft above the water surface.