If you’re looking to pump water in a rural setting there are a lot of options that can be used, however, not all pumps are created equal. Some are more expensive than others and may require outside funding, and others can be built from locally available parts that are fairly inexpensive. Some have a lot of working parts which make maintaining them a challenge, while others are very simple and easy to maintain. Further, some are designed to give enough water for one or two families while others are designed to provide for an entire community. This article is the first in a series where I will talk about several different pumps and how they measure up. Hopefully this information can find its way to the people on the ground installing pumps and help some people gain access to sustainable water. Today I’ll be writing about two different pumps: the Rope Pump and the No. 6 Pump.
The Rope Pump
The Rope Pump is a rotary hand pump that has been around for a long time and is based on the ancient Chinese water lifting principal of the “chain and washer pump”. More recently, it was refined and gained popularity in Nicaragua in the 1990’s. Since then it has gained popularity around the world, with different countries modifying the basic design to fit their specific conditions. As you can see from the picture below the rope pump has few parts, which makes it ideal for low-income rural communities since the pumps can be manufactured locally, maintained, and repaired at a low-cost. Further, the simple design means that it is easy to use, and the people using the pump will most likely be able to perform the maintenance on their own once they’re shown how the pump works.
So how does the pump work? At ground level there is a stand with a pulley wheel and a handle. When the pulley wheel is turned it pulls a closed loop of rope that has pistons attached to it through a rising main pipe that has the lower end submerged in water. As the rope is pulled the pistons grab the water and raise it up in the pipe until it gets to the surface where a spout is located to let the water out. And that’s it!
Rope pumps are mainly used in more shallow, hand dug wells (0-20 m), however, they can be used on boreholes of greater depth with a little extra work. Also, with some modification they can be used to pump water into a storage tank instead of out of the spout. In its basic form, depending on the depth of the water, a rope pump can discharge up to 40 liters per minute!
Certain designs use car tires on the pulley wheel for friction on the rope, but if you are just using a bare metal wheel you can scratch up the surface of the pulley wheel to create friction and keep the rope from slipping.
If you want to get creative you can attach an engine to run the pump, add a stationary bike to pump instead of turning the handle by hand, create a wind powered rope pump, or even an animal powered rope pump.
You can either get pre-manufactured pistons, a more expensive option, or you can use an old car tire and cut the pistons out of it. If you choose to cut them you need to make sure the pistons are all the same size. This can be done by using something like a pipe that has been sharpened as a cutting tool.
Pay attention to pipe size. The deeper the water is, the smaller the pipe size needs to be. To understand why think of a 10 m length of pipe and a 30 m length of pipe, both the same diameter, and both filled with water. The weight of the water in the 30 m pipe is going to be three times as much as the weight of the water in the 10 m pipe, and therefore, could be very hard to rise to the surface. However, if you use a smaller diameter 30 m pipe then you will have less water weight and can more easily bring the water to the surface.
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All things considered, the Rope Pump is one of, if not the, least expensive and simplest type of pump available. Its simple design along with its ease of use, maintenance, and repair also make it ideal for rural settings.
No. 6 Pump
The No. 6 Pump has a little more to it than the Rope Pump, but is still fairly simple. However, it would be hard to create all of the parts for the No. 6 Pump without a local craftsman (some parts must be cast iron), which means that it is more expensive than the Rope Pump. The No. 6 Pump is a lever operated suction hand pump which is typically installed on a tube well (but can also be installed on a dug well), and is popular in Nepal, Africa, India, South America…pretty much everywhere.
So how does it work? The pump consists of a handle, piston, rising main, base valve, and cylinder. When you pump the handle it moves the piston up and down. When the piston moves up it creates a vacuum which lowers the pressure below atmospheric pressure and the water fills the empty space. Then when the piston moves down the water passes through the piston. Now, with the piston below the water, it is raised up causing the piston valve to close, and the water to be expelled out of the spout. At the same time the base/check valve opens to allow more water to fill the empty space. Here’s a good visual representation of this process:
And a technical drawing of the No. 6:
No. 6 Pumps can only pump from shallow wells (6-8m) which may limit its use in some places. Once the tube well is installed the installation of the pump is fairly easy and doesn’t require any special tools. The only maintenance that is required is the periodic replacement of valves and seals which can be done with simple tools by someone from the community that is elected to maintain the pump. No. 6 Pumps can serve the needs of 50-100 people with an output of about 4.5 cubic meters per hour.
The No. 6 Pump must be primed before its first use and anytime the well goes dry for any reason. This is done by pouring water into the pump head until it is full. Be sure that the water that is being poured into the pump head is clean water, otherwise it has the potential to contaminate the well.
Because this pump has cast iron parts, valves, seals, etc. if something breaks it could be expensive to fix and difficult to find the parts unless someone is manufacturing them locally.
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The No. 6 may be a bit more expensive and require a little more know-how, but with millions in use around the world it seems to be a good choice if funding is available and manufacturing is done locally. It’s an easy to use pump and gives the opportunity for an opportunity for someone in the community to take responsibility for the maintenance and repair.
No one pump is the overall best for every situation. Like most things in life, each pump has its good qualities and its bad qualities. In part 2 I’ll look at a couple of other pumps (I haven’t decided which ones yet), and see how they stack up. If you have experience with either the Rope Pump or the No. 6 Pump I’d love to hear about your experience with them and how it went, especially if you had problems. In the sources below you’ll find some documents that can be helpful if you are planning on building one of these two pumps. Hope they’re helpful. As always, thanks for reading, and I’ll see you next time.