Getting water out from a deep well is not as simple as one would hope. This article scratches the surface on the various difficulties that one would face when trying to extract water from a well that is more than 10 meters deep and will explain how the can be easily avoided by using a rope pump.
So, if you read the Manual Water Drilling / Well Drilling article and you got excited about digging your own deep well, you will soon discover that there is one more detail that you have to figure out – how to extract the water. If your well is more than 10 or even more than 8 meters deep, you will find out that it is not possible to use a suction pump. Why? Because every 10 meters of water column increases the pressure at the bottom of the pipe with one atmosphere. Now if you look from the perspective of a suction pump, you will be trying to lift more than 10m water column – the pipe that goes into your well filled with water. However the downwards pull of the water in the pipe will be greater than the atmospheric pressure at the exit of the suction pump, therefore the suction pump will be only trying to create vacuum. When you add the various losses from the operation of the suction pump, it turns out that the practically achievable depth of operation of a suction pump is around 8m.
Now, as we ruled out the first solutions that came to mind, we need to make a list of what will really work:
- Submersible pump – Most of these neat devices work by utilizing vibration to move a membrane that in turn pumps water upwards from the depth of the well. As it turns out, it is much easier to push water than pull water. The drawback is that you need electricity for this pump to work and also you need a well that is wide enough, so that the pump can be lowered to the bottom.
- Deep well hand pump – These devices have a lever that goes all the way down through a sucker pipe to the piston located at the bottom of the well, where the actual pumping occurs. The design of the device seems quite simple and doesn’t suffer from the disadvantages of the submersible pump mentioned above, however building one of these on your own might prove to be a tricky job, due to the great forces and pressures involved.
So we get back to an old and often overlooked solution – the rope pump. This pump consists of a rope that goes down the well and then up through a thin pipe. The rope has knots which are nearly as big as the inner diameter of the pipe, so when the rope circulates, water gets trapped between the knots and lifted to the surface. While not looking trustworthy at first glance, this type of pump can achieve 85% efficiency, while being easy to construct and repair. You can find more details here and you can find a detailed manual on how to build one of your own here.