Automatic Switch-Off for Electric Water Pump

A common item here is a sump pump (to remove water in basements). A spring-loaded arm on a switch supports a bead chain with a float on it. When the water is high in the sump, the float's weight is off the arm and the pump starts; when the level drops far enough, the hanging weight pulls the arm down & shuts it off again. If the chain went under a pulley low in your tank, so that the rising float pulled the switch arm down ("off"), and the float provided slack in the chain when at a lower level, permitting the spring to raise the arm to the "on" position, you'd have an automated system.

Thanks- for suggestion, is it possible to give sketch, to make it more clear.Kumar.

I think so: will try tomorrow, when I have access to a scanner. Ron

Keep in mind, that basement sump pumps are submersibles. Something tells me that is not true for your situation. Your water tank...open cistern, or closed? (It seems likely that the water is elevated to provide head pressure, but I wouldn't want to assume there are not other reasons. What I mean by that is, if there's electricity to elevate the water reservoir, there's also electricity to compress the water in a ground-level tank. Irrigation or potable water supply? Is the switch mechanism going to turn the pump on as well as off? Or just off? I didn't quite get that? These details will help to get a better handle on your situation and the possibilities that might work.

A mercury switch in the tank of water will switch the pump on and off

The simplest way for home amatuare is to use 2 SS
probes approx 10" long pierced through Rubber Cork of flask & hanged [suspended] from topof water tank so that lower tips R just an inch below the top level of expected of water. As soon as water touches the tips of probes an electrical short cicuit is generated. This may be used as sensor in an electronic cct. Pump motor is started thru a Push-Swith which actuates a relay to start motor & relay is "Held" by electronics & the sensor causes to break "Held" relay.
If needed I can send the circuit I am using for just the purpose.

Here, we use a pressure tank for our wells. The well pump will pump water into a pressurized water tank. Typically, the tank has an air bladder on the top half and the lower half fills with the well water. The bladder's static air pressure is set at the factory to match the desired pump shut off pressure. A pressure switch simply turns off the pump when the water pressure reaches its upper set point and turns the pump on again when the water pressure hits the lower set point.

To prevent water from back flowing into the pump, a one-way check valve is used between pump and tank.

The concept of using the tank is to act as a capacitor for your domestic water supply. Pressure is maintained within the two limits (upper and lower) and the cycle time (time between each start of the pump) of the well pump is reduced.

If you have city water (no well) the city water system is pressurized and no holding tank is required.

It sounds like your holding tank is located on the roof and the water pressure is gravity supplied. The pressurized tank does not need to be above the point of use and can be located many floors below the outlet source.

If you are stuck with a gravity system, check out how a basement sump pump works. They use a float sytem much like a standard American toilet. The difference with the sump pump is the shut off is acomplished electrically with a switch that is tripped by the float.

If the holding water is to be used as drinkable water you need to consider components that will be approved by all local laws and regulations.

Thanks for all the info. I will try a float to operate electric swith. thanks and regards. m m kumar

With all due respect to Ron and AC, I'm having diffulty picturing a float-lever arrangement that would be anything other that unreliable and a possible nuisance. A better idea might--possibly the other guys might agree--be one that borrows from both Ron's and AC's suggestions. Depending on the elevation of your tank (the head pressure, that is) it might be feasible to install a "down pipe" into the tank and a pressure switch at the bottom of that pipe. Depending on the water level in the tank (the pressure at the bottom of the pipe), the pressure switch could energize and/or de-energize the pump motor. If that could be done, you would not have to go up to the tank to make adjustments or repairs. The switch would not be subject to wear and tear, or water movements, that might cause unsatisfactory results. A well pump dealer might be able to offer suggestions and parts to help you do this.

In every automatic washing machine there is a sensitive pressure switch, a tube leading to a capsule with a diaphragm inside, to tell the machine when there is enough water in the drum. You can recuperate one for nothing, to try this out. Connect the tube into the bottom of your tank. Fill the tank to the correct level. Lift up the pressure-switch until you hear it click. Lifting and lowering it, you will find a good threshold level. Fix it there. Connect your supply pump in series with the switch. The only problem I can foresee is that the contacts will burn out under the heavy current draw of the pump. It would be good, therefore, to mount a relay/contactor to do the hard work. This is cheap, try it !

...compliments, Labinbleu, on an ingenious improvisation of the pressure switch idea. I am wondering how easy it might be for Kumar to obtain the washing machine components...if he can't locate a "rehab" machine easily...or is unwilling to buy and sacrifice the machine in order to have the sensor. Perhaps you could suggest a source--or an exact nomenclature in case he wants to order new from a manufacturer. I am not as familiar as you about washing machines, so I wonder if the washing machine sensor would be robust enough for Kumar's water tower. (The washing machine's water depth at the sensor would be less than a meter, it seems to me, while... Kumar did not state how high his water tower would be; what the head pressure is. My idea was that a well service supplier would be able to provide the pressure switch (which would be adjustable) as well as the relay and contactor assembly...for Kumar to utilize in an application that is essentially the same as a well pump control.... There would be no need to scavenge anything, the components would be sure to have the necessary ratings; a specified enclosure box would also be available...all from one source. The only labor would be mounting and making the electrical connection. I would guesstimate that the cost would not exceed 50-100 USD. Also, depending on Kumar's location, there is one problem that can come up with ground mounted switch enclosures: insects--they seem to like getting in and shorting themselves between electrical contactors. Periodic inspection, and calking around any path from the ground into the box can minimize this problem pretty well. Another advantage that comes with well type motor control components is that they are usually fitted with overload cutoff breakers to prevent motor damage.

But I would really interested to hear that the washing machine could be adapted even to much higher head pressures. By the way, where did Kumar go? Sure hope he didn't fall into his water tower. Someone ought to go check on him.

Hello, CowAnon, and Kumar too, if you're still out there. I lived in Ireland for many years, and in general we were poor, so the first solution that comes to mind for any mechanical problem usually involves components from scrap-yards, back-yards... We often found that ready-made devices would not work for long in the field. It's all very well to design and test something in a warm, dry workshop, standing on insulating duckboards... My idea with the washing-machine barostat was that it would be mounted beside the tank, so that the pressure head would be very low - in a real w-machine this is typically 500mm. I was presuming that K is both poor, and fairly handy... Example - We had trouble with outdoor and underground electrical connections - the "Waterproof" boxes being better at keeping the water in than keeping it out. Solution - fill them with hot pitch. Critics said, "what if it goes wrong?" The truth is that if it never goes wrong you don't ever have to touch it again. I feel strongly about this - how often have I seen technological fixes by well-meaning "First-World" engineers fall by the wayside in "Third World" countries. I include Ireland in this latter category... and remember that $100 can be a lot, depending on where you live. Have a look at our group on http://groups.yahoo.com/group/howthingswork/

Have a look at our group on http://groups.yahoo.com/group/howthingswork/
--
"A problem, properly stated, is a problem on its way to being solved" -Buckminster Fuller

Thanks, Lapinbleu,

Buckminster Fuller, heh? Brings to mind my childhood sojourns in St. Louis, traipse-ing around the Missouri Botanical Gardens (Shaw's Garden) and looking at, sometimes going inside, the tropical exhibit in the geodesic dome, one of Fuller's early projects--I think it was, in fact, his first--before he went kinda whacky.

I can appreciate your point about poverty and handiness, but I'm hard pressed to envision how anyone who could post a message--who could afford to pay for the hardware & software--and pay for Web access--and pay the various associated middlemen and "hangers-on"--would fit in that category: where less than $100, or even less than $50, for a durable property-improvement fixture, would impose an overwhelming burden. Based on grim experience, I had also hoped to suggest a way--a relatively easy way--to avoid being "penny wise and pound foolish." And a way to obtain ready, local expert advise.

And I agree with your view that--in some cases--old things are more rugged than newer things, and that "laboratory testing" does not always translate as it might to field utilization. However, well pressure switches have already proven themselves to be very reliable, in the field, under all unsheltered and semi-sheltered, ambient conditions, for very many decades--with virtually no change in design. The same holds true for semi-sheltered well pump switching relays and contactors. In contrast, washing machines are designed for only indoor or sheltered environments--and designed to last only a few years, not decades and more as is the case with well systems. Consider also the design duty cycle of even older washing machines, as opposed to that of well pump controls. Another thing is that washing machines are well known to fail in the "unsafe" condition--to cause overflow flooding. Well pressure switches are designed to fail only in the pump-off condition. You also mentioned that the pressure switches in washing machines are diaphragm type. One might conclude they might be subject to inaccuracy &or diminished reliability if exposed to extremes of changing outdoor conditions. But, perhaps not. Another factor is ease of installation and maintenance...and safety as well. By affixing the mechanical and electromechanical components on the elevated tank entails going up off the ground...both to install and maintain; and to bring the elevated "hot" electrical fixture in close proximity to the water. With the more robust well controls there is no necessity to carry electrical service up from ground level. There are no moving--no wear-out--parts at tank level that will ever require mounting the tower for maintenance. So safety would be enhanced. It is also possible--if K and his neighbors are presently pumping groundwater--that K already has some of the equipment he would need.

Thanks for the URL to the How it Works forum. I will be checking it out.

Either get the float and switch for a pedestel sump pump, available at the hardware store and mount the switch upside down, so to fill the tank or go to sump watcher site and look at the washing machine cut off switch. Will shut off power when the water touches it and just reset to pump again.