Static Water Level in Well - Stone Drop Method

[Carl_NH]

Saturday AM - could not figure out why irrigation didnt run... Hmm took cap off well and can hear the pump running even tho I thought there was no water being drawn, so dropped a stone to check the water level - 15 seconds or about 350' is static level - this is lowest I have ever seen.

Long story short wife left the valve open on 200' of manual drip irrigation for 20 hrs Fri-Sat AM.

So solved that problem but lingering issue now is the pump likely ran dry when I thought we had in excess of 10 GPM flow in the well. (don't have a low pressure cutoff switch installed but will by tomorrow!)

My question is determining the static water level using the stone drop method. As close as I can tell by my searches is its about 24' per second so @ 8 seconds = 192' to the water level. Is this accurate - what do you water well guys/gals say?

The well is 6" casing, 410' deep, pump is 1.5HP 10GS15 Goulds set at 375' +- so my next step this AM was to monitor the static depth when irrgation was running. At the beginning of the cycle the water level (by my stone drop test) was 5 sec or about 120' to static water level. At the end of the cycle, 13 sec or 300', then 30 minutes later after the end of the irrigation cycle the level was 8 seconds or 190'.

What this told me was the recovery (300'-190=110x1.5 Gal) rate in 30 minutes was roughly 165 gallons or 5.5 GPM is the flow rate of the well.

What will skew the numbers is if my estimate of 24' per second is accurate on the stone drop test..

A little more detail on the well is when it was drilled (thru 400' granite) it produced 1.5 GPM, so we had it hydrofracked and after the fracking it was reported "over 10GPM". So the other question is can or does a hydrofracked well "close up"? Can it be fracked again?

Thanks in advance..

 

[Mickey_Fx]

Don't think you want to be dropping rock down the well as you never know what can happen at the other end.

Think you need to find a better way to measure water depth. A method I use was to measure by pressure. Run a length of tubing down the well to a known depth (add a weight to the end so it will keep the tubing straight). Water weighs .43 lbs per ft of depth. At the top end have a pressure gage and schrader valve attached. I always pressurized i.e. purged the tube a little prior to taking a reading to make sure if there was a slight leak in the tubing/fittings I'd purge the water from the tube and get an accurate reading.

Check the pressure on the gage, now its time for a little math. Pressure X 2.325 = water depth from lower end of the tube. Subtract that from depth of tubing in the well and that give you the the static water level. You do need to have tube as short as you can above the well head to make the measurement as accurate as possible.

 

[SPIKER]

Those stones can wedge your pump tight when time comes to pull it and can also cause issues. Low pressure switch is good to have and running modern pumps without water flow is not as bad as days past, motor and pump are below the intake level so they stay submerged and cool in the well water. Though doing so can lessen the pumps life with seals and such not getting full water pressure cooling/lubrication. n

A better method it to get a fishing pole and use some braided line that absorbs water, (not fishing line but a cotton masons line type material to drop into the well. The Gauge method is great too but cost for a long length of tubing is pretty high to get 300+ feet of tubing vs 350 or 400 feet of the cotton line. mark line at the top of the casing & pull out until the wet line comes out and use measuring wheel.

Mark

 

[KTurner]

As close as I can tell by my searches is its about 24' per second so @ 8 seconds = 192' to the water level. Is this accurate - what do you water well guys/gals say?

Ignoring the well aspect of this and just looking at physics... Something falling does not fall at a constant speed. Gravitational acceleration on Earth is 32 feet per second per second. At the end of one second, your rock is going about 32 feet per second. At the end of two seconds, your rock is going about 64 feet per second, three seconds is 96 feet per second. And so forth. At some point, it will reach terminal velocity, where the air resistance keeps it from going any faster. This will depend on the object in question. A feather and a marble accelerate at the same rate, but the feather reaches its terminal velocity much sooner than the marble.

Keith

 

[Carl_NH]

Thank you gentlemen for the replies.

Kturner On the speed of a rock falling - per your analogy after 3 seconds the rock would have traveled 32+64+96 = 192' so I cannot imagine how that is possible.

On the tubing - I understand that but finding 300 or so feet of 1/4" tubing may be a challenge and costly especially if its the soft pliable type.

Then the string/line method with a weight on it is something I have done before but one issue is the line tends to get entangled with the wire. I might try some nylon line with something thin attached for a weight. I have used a 100' nylon tape measure with success in the past with a small wrench attached when the water level was higher.

On the rocks - these are 1/2-3/4" pebbles and the only thing that they would lodge on is the torque arrestor above the pump and when it cycles they likey would get dislodged falling below the pump. The 4" pump has a SST screen around the intake as well.

 

[Egon]

The formation fractures can plug up. It should be possible to do another frac.

 

[V1Rotate]

Instead of dropping a stone into your well, how about dropping an ice cube?

 

[Carl_NH]

Update:

Havent used much water since this AM, so I went out with my nylon 100' tape with a small wrench attached for a weight. It hit water at 56' so I then dropped a small 1/2" stone - took 3 seconds to hit the water. so rough calculations would be around 20' per second. Excluding acceleration - I still need to noodle on that..

The pitless adapter is 6' from the top of the casing so this means the pump is sitting in 325' of water or almost 500 gallon reserve.

By the way, I have now dropped 5 pebbles in the well in the last 2 days..raising the water level - I like the ice cube - GREAT idea!

Egon - thanks - i will speak to the driller Tuesday but for now I am going to cut back on the sprinkler use and let nature handle it until I get more info.

 

[Egon]

Distance equals 1/2 times acceleration times the time squared. assuming zero for initial velocity.

D=1/2 x at**

 

[Carl_NH]

Egon,

I didn't do well in Algebra in school - can you provide an example with the information given?

What I have seen on the web searches 9.8 meters/sec is the rate at which a object falls less the speed of sound traveling back but that doesnt compute with my measurements.

Thanks!