well depth sensor

[alternety]

I need to monitor the depth of the water in a 600' deep well. Since I destroyed the pump head yesterday I have an opportunity to install something.

The best idea I have seen from the maintainability standpoint (everything is above ground) is the bubbler approach. Run a tube down, bubble air thtough it slowly, measure pressure of air supply.

I am open to other approaches, but my current question is about the air supply. I would need a reliable, low maintenance very low volume air supply. I saw one post that talked about aquarium pumps but with my depth I need around 260 psi. I suspect a different pump is called for.

Anyone have a suggestion for an inexpensive solution to the air supply?

 

[stevez]

It would help to know the volume of air used as that will impact the compressor size.

Keep in mind that the air pressure needed is related to the depth of probe submergance below the water line. 260 psi suggests that the well can run from 600 ft to zero. Maybe you don't really need 260 psi.

 

[alternety]

Yes the well can vary through that range.

The air volume is very low. Enough to just make bubbles come out the end.

 

[philba]

Interesting problem.

Is the bubbler necessary? How reliable is 600 ft of tubing going to be? How much will that weigh and can it support itself? Heck how much will that cost? I do think a pressure transducer makes the most sense for this application.

I wonder if sensing the pressure of the water being pumped out would work. I assume that you will get more pressure (less?) when the water is at 10 ft than when it is at 600. I assume that the difference is going to be related to the water height.

Another thought - I have a controller for my pump that senses over and under current for different situations. Will the pump have to owrk harder to pump 600 feet than 10 ft? I assume so. That should translate into a different current draw.

I'm not sure how you would calibrate either of those approaches.

 

[alternety]

If I don't use the bubbler I have to put down a sealed tube with a diaphram capable of transferring the pressure to the internal fluid (air?) and thus to the pressure sensor on the surface. And I suspect the tube will have to be ridged to resist affecting the results. That seems failure prone and difficult.

The pump current does correlate to depth of pumping and I have some data on the curve. However, I am trying to watch recharge rates and static levels. Starting and stoping the pump to sample depth is not OK for a number of reasons.

Putting the pressure sensor in the bottom of the well is certainly the most straight forward approach, but it requires a sealed and corrosion resistant unit (many hundreds of $ from what I have found). And if it breaks I am out of luck. Getting things in and out of the well requires a well drilling rig and a lot of time and effort. Thre is 600' of water filled 1.5" pipe, a pump, 2400' of #6 wire and a couple of #14 wires. Each 20' section has to have the wires removed from the taped on positions, and be unscrewed.

 

[tunedwolf]

if you use a sealed tube, you will run into all sorts of troubles with temperature etc...

 

[alternety]

One other little point. I have only a few days (I hope) to decide and acquire whatever is going down the well when the replacement pump arrives.

 

[john1]

Hi Alternety,

Interesting situation.
I presume that there was not an existing method for determining well
level ... ?

If you have considered various other methods, and you have decided that
the 'bubbler' technique suits you best, then i suggest using a pump
from an old kitchen refridgerator.
Or from an old shop freezer unit, or some commercial cooler display
cabinet.

They run happily in the pressure range that you mentioned, and they are
designed for very long service life, and to run reasonably quietly.

Such a small 'motor-compressor' would be overkill for a small domestic
well, but for what you describe it might fit the bill. The volume of
delivery from these type of pumps is quite low, but you may have to
throttle it back further, to suit yourself.

Another possibility is that you may not need continuous indication of
the water level.
If your well takes a long time to fill before being pumped out, then
maybe a bicycle pump would do the job, perhaps each day?
Or maybe morning and night ?

Every hour would be too often to pump up with a bicycle pump, but it
might be Ok to do it with a small fridge-pump.
Don't forget to allow the reading to settle, there might be a lot of
water to push through the sensor pipe before taking the reading.

Best of luck with it, John

 

[tunedwolf]

if this is for pump protection, why not just use a flow switch and timer at the pump outlet ?

 

[alternety]

NO. I want to track the water level.

 

[john1]

Hi Alternety,

Ive just been out into my garden, to look at an old 'Fridge-pump' that
i thought was still there. It is still there, i took a couple of pics
just to show you what they look like.
They are sort of a 'sealed' unit, at least on the pump side of the
unit. On the motor side, its a brushless motor, and pretty much sealed
but not as well as the pump side of the unit which contains its own
oil-bath and does not normally meet the external environment.

This particular unit has been sitting around in the dead leaves in the
garden for a long time, if i wanted to use it, i would clean it down,
check the motor over with a meter, and i would expect it to run.
And i would expect it to operate.
They are very hardy little units.

This one was picked up from a skip ( i think Americans call them
dumpsters ? ) and used for a while, then put to one side.

The pictures are just in case you don't know what i am talking about.

Best of luck with it, John



**ive just seen your last post, maybe you missed my earlier post ? ***

 

[john1]

Hi Alternety,

You mention you only have a few days to settle on whatever is going
down the well when the replacement pump arrives.

If you have decided on using a 'bubbler' then all that has to
accompany the new pump assembly is a suitable length of tubing.

If you use it fine, if you don't then its not such a loss.
But if you don't put something there to use then you wont have any
way to monitor the level, unless you use a length of string with a
bit of wood on it.
Some people do.

So in your position i would plan to include a suitable tube to be
installed at the same time as the replacement pump.
The rest of the sensor can be attended to above ground, and when it
suits you.

Best of luck with your well, John

 

[alternety]

Refrigerator compressor - now that is interesting. That is the kind of idea I was looking for. They look different here (in residential units anyway) but same idea. One complication here is the freon police. I believe it is a federal crime to vent freon by tearing a frige apart. If you watch world news you can see that you really don't want to annoy our current federal govenrment.

I did not realize they developed that amount of pressure . I want to do some tracking initially every few minutes to see what the characteristics are. And I will probably do that every now and then. Otherwise I really only want to see much data when the pump runs and for a while after. Obviously a bit of control work there but that is fun.

I am concerned about the well. It is for the retirement house we are almost finished building. We drilled 620' through solid granite. No aquifers at all. At the end my kidneys and a six pack made water faster. Hydrofracted it and now it does about 3 GPM. But I have no idea where the water is comming from (well, cracks in the rock, but overall?). I really want to characterize the thing so I can make a reasonable guess at wheather or not I can get enough water for fairly extensive gardening.

 

[philba]

Interesting problem you have. 3 GPM isn't enough to run sprinklers, maybe enough for drip irrigation, though. You might need to pump into a holding tank and then pump from there for sprinklers.

I have a spring on my property, it runs at around 5 GPM. So I get approx 7200 gallons a day. It flows into an 8K gallon tank and I pump water from the tank. We've got around 2 acres under irrigation and use about 2/3 of the tank on the hotter days. This gets consumed in about 4 hrs of watering. we use a lot of drip irrigation. we have a pressure tank and use the pump to pressurize the system.

 

[stevez]

You might break this into two part:
1. Characterizing the well.
2. Monitoring for pump protection.

You might use high pressure nitrogen or compressed air (stored at 2000 psi) from cylinders - thru a regulator- controlled by a solenoid - to make periodic measurements. Sure, you'll use some air or nitrogen but once you get the data - maybe that will be enough.

You might then use more modest pressures on a continuous basis - from commonly available,low cost compressors that run easily at 100 psig, to alert you and also to indicate water level that is from 0 to 200 ft over the pump.

If the well actually fills to the top could it be groundwater that is getting in - and if that is the case - is that a problem?

 

[alternety]

I appreciate the well intedned (sorry ) cmments. They system is done. Pressure tanks, oressure pump, and storage tank are all in place. Well pump has protection. Filter is filtering. Toilets flush if I can get a working pump.

The pump can empty the well. The pump is protected. I want to see flow rates into the well and a history of this flow and static levels to project the prpbable long term performance. That is all this is for.

The well scares me.

 

[tunedwolf]

if you were to fall into the well...you could always count the depth in feet as you sink

 

[john1]

And have you any facility to monitor the depth of water ?

 

[alternety]

I do not have anything to measure depth. If I had time I would consider an absolute sensor at the bottom. Not enough time. The tube for a future bubbler is the only thing I could think of. Eventually, once I get in the house and finish other more directly pressing issues, I will work out monitoring.

If I get a shop air compressor with sufficient pressure I can fill a tank and let bubbles leak from the tank. Needle valve or something. Will have to look into details later.

Off the top of my head I will need to look for a flat spot in pressure (delta p = 0)from the comperssor and read that as a depth. When pressure starts moving again I will have to follow it. Sample points are going to depend on rate of change of water level and air flow volume. Higher air flow smooths the samples. I will probably have to supply some intelligence with a microprocessor in the loging system.

It will give me something to amuse myself.

 

[grim]

could you not just bounce an ultrasonic pulse of the water surface, and time the echo? like car parking sensores?

or use the laser measuring things that black and decker sell?