you can extend a sand point to 50 feet down. You need to make a slight change. You will have to install a foot valve at the top of the sand point and a check valve at the base of your pitcher pump. If you are using a standard pump you will have to install the check valve at the discharge of the pump. It will take you a longer time to prime it to get the well pipe full of water and to get the air out. It will work I have done it before in a pitch.
When I suck on the straw, I am creating a low pressure area inside the straw, and the atmosphere pressing down on the liquid forces the beverage up the straw....It also occurred to me that capillary action would prime the straw,
that is our definition of "sucking" and how we mechanically understand it. creating a void that the laws of nature dictate must be filled.
1 atmosphere of pressure is equivalent to a water depth of 33 feet. (In other words, every 33 ft under the water you go is like stacking an additional Earth atmosphere on top of you.)
The "suction force" can only ever be as high as the pressure pushing the air into the hose...For a 3/4" conduit, its max is 6 lbs of force
the vacuum is simply a vacant space. And when you expose that vacant space to an environment, the environment is actually pushing itself into the vacant space. So suction isn’t a vacuum pulling air into it, but air pushing itself into the vacuum.
Because the vacuum isn’t really pulling anything, the water can simply only push itself so far.... So once you get 33ft of water it exerts the same amount of force downward as the air does [upwards] and no more movement is possible.
Negative pressure in water actually goes below vacuums since the electrostatic properties of water pull on itself and it’s container. ...That’s how trees can grow so tall. Without this negative pressure, plants could only grow to 33 ft since plants dont really use positive pressure pumps.
You maintain the liquid column height by pressure differential between the top and bottom of liquid, and the maximum height can be achieved when the top is at perfect vacuum.
Since the atmospheric pressure is 1 atm / 14.7 psi / 101325 Pa, the maximum height is determined by below:
(Pressure, P) / (water density, rho x gravitational acceleration, g)
Plugging in the values (I'll use SI units, with pressure units converted to SI base units):
(101325 kg(m/s2)/m2) / (1000 kg/m3 x 9.806 m/s2) = 10.33 m = 33.9 ft
This height changes slightly with temperature, due to its effect to water density.
But as your column of water gets higher it gets heavier. At a certain point the column of water reaches a height where it is heavier than 1atm/14.7psi and can no longer be pushed up. This is right around the 10 meters mark and that would only be the best vacuums/pumps in the world.
So there's NO way the first claim is correct that a foot valve enables atmospheric pumping of water up more than 30 feet!
However it would be worse than that because of vapor pressure. Think of vapor pressure being the pressure water exerts on the gasses surrounding it. If that vapor pressure is larger than the surrounding pressure, then the water boils! For example at 212F water’s vapor pressure is 1 atmosphere of pressure.
Let’s assume your well water is 60F, then it’s vapor pressure is 0.0174 atmospheres, which is equivalent to 0.58 feet of water.
That means if the pressure in your hose goes below 0.0174 atmospheres, the water will boil!
So what does this do to your pressure differential? It becomes atmospheric minus your vapor pressure so approximately: 33 - 0.58 = 31.42 feet of water.
I’ve seen some mention of negative pressures, just want to emphasize their is no such thing as negative pressure.
let’s use Bernoulli’s equation. If we simplify a bit, we’ll get P1 = rho x g x h. P1 is atmospheric pressure, rho is 1000 kg/m3, g is 9.81 m/s2. Plug that all in and solve for h and we get h max as 10.32 meters, or 33ft, 10 in. Now we won’t be able to recreate a perfect vacuum but we can get close, resulting in somewhere around 32 ft
1 ATM = 14.696 psi (lb/in2). 14.696 lbs of water has a volume of 387.518666 in3; divide by 1 in2 (per square inch), and you get 387.518666 in, or 32 feet, 3 33⁄64 inches.
So on the ground the air pressure is ~ 14.5 PSI.
When you remove air from a 32 foot tube whose end is in water, the water is pushed up by this 14.5 psi. When the weight of the water = 14.5 PSI the atmosphere cannot push the water up any further.
If you perform this test on Mt Everest, the air pressure is < 14.5 PSI so the water column will be < 32 ft.
P=F*A so, let’s assume area to be 1m2 for simplicity, you would be able to “supply” 101.325kN of force into the water, so that is how much force is “available” to lift the water.
101.325kN of water is equivalent to 10332kg of water which is 10332 liters which is 10.332m3 worth of volume of water “sucked” into the tube.
If adding gas to the fluid halves its density, you could pump at about twice the depth.
https://petrowiki.spe.org/PEH:Sucker-Rod_Lift
Is this what a Sucker Rod pump does?
This is partly how oil wells can turn into blow outs while drilling.
If you introduce air, it might be more similar to a vacuum cleaner, where you are relying on the airflow to dislodge and carry particles. For example, if you hover a vacuum cleaner nozzle above a puddle of water it will suck it up, but if the nozzle is pressed against the ground with no flow, the water under the nozzle will stay....
I have done this in practice- sucked water eighty feet vertically with a vacuum pump at the top. Required a six-inch hose, a VERY powerful pump, and could only lightly 'sip' the water with it. But it did work.
https://inspectapedia.com/water/Well_Pipe_Foot_Valve.php
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