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I'm trying to recreate a phenomenon I have noticed from our water tank at home. Ok so we have a deep well pump that fills our water tank everyday. But something odd always happen everytime the water tank is full. The tank has an outlet(actually just a pipe sticking out of the tank) where the water spills out when the tank is full. This is when the phenomenon happens, when we turn off the water pump the water will keep spilling out of that outlet pipe FOR HOURS! Even though the water pump is already off the water will keep spilling out of that outlet pipe. The only proven method to stop the water spilling is to turn on the faucet in the house meaning to use the water. Once when I was alone in the house and the water started spilling after the pump was turned off, it was 6pm, I waited it out and see if it would stop by itself. I waited for 2hrs, finally I had to turn on the faucet in the house around 8pm to stop the water from keeping on spilling.

So here's what I was hoping to do. My mom has been complaining about the high electricty bill. One of our highest electricity usage is the water pump since it takes an hour(more or less) to fill that tank with water. And we fill it twice a day since we run a room for rent business. I was hoping I could recreate that phenomenon and build a tank(a smaller one of course) on top of the main tank. Then all we have to do is fill that new tank with water for lets say 15mins and let it spill water into the main tank for the entire day.

Here's a link on a diagram of our water tank.

Hope someone can help. :)

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I suspect that this is would be better on the Home Improvement site (if they want it as there is unlikely to be anything deep going on in the physics realm here. It's just a question about how the system works. – dmckee♦ Mar 1 '12 at 18:08
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As you've described the situation, this should be impossible. There must be something else going on. My first thought was that the pump was starting a siphon, but since the tank outlet is above the water level in the well, a siphon is impossible. Maybe your pump, or the electronics that control it, is broken? – Colin K Mar 1 '12 at 18:10
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It sounds impossible to me as well. If the outlet pipe is small is it possible that the pump fills the tank to well above the outlet and it then takes a long time to drain back down to the level of the outlet? I think you need to look inside the tank to see what's going on. – John Rennie Mar 1 '12 at 18:16
It would not make much sense, but if the outlet pipe is going into the tank you could have some kind of siphon effect and that might run for a long time until you disturb the flow by opening a faucet. – Alexander Mar 1 '12 at 19:07

1 Answer

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I think this is what is happening, though your diagram may conflict with this. Have you opened it and looked inside? Or is this diagram drawn only by looking outside?

Many tanks have a device that opens the overflow pipe when the water reaches a certain lefel. They consist of an air-filled ball attached to a lever (it's called a tank ball iirc). When the ball is pushed up, the overflow pipe opens.

Your ball-lever mechanism may be getting stuck. If the outlet is low enough, and the ball-lever mechanism is near the top, the overflow should be getting activated once the water has already crossed the outlet and reached the top. If the ball gets stuck, then all the water from the overflow outlet to the top will spill out.

I don't know how turning on the faucet solves it. Unless the faucet outlet is connected to the lever via a valve in such a way that it is preferentially used as an overflow (pretty reasonable, you may want to simultaneously fill and empty it.. Though it may be too much ado for nothing.

Open it and check first. If its as you described it, modify the tank and get free energy ;D.

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