Thanks to everyone who read and/or commented on part 1. Your feedback is always appreciated. If you missed part 1 you can find it here. Today I will again talk about two different pumps, one that is fairly simple, and another which is a little more complicated, but still fairly simple. So without further adieu…
The Treadle Pump
The treadle pump is a simple suction pump that has been around since the 1970’s. It was first introduced to farmers in Bangladesh, and it quickly gained in popularity. All of the sudden farmers were no longer dependent on rain fed irrigation, and could now grow two rounds of crops per year. Since then it has spread throughout the world with over 2 million installed, however, the majority of the pumps are located within Asia.
The treadle pump is foot operated and works by stepping up and down on the treadles. This action causes the pistons within the cylinders to move up and down. The up-stroke creates a vacuum and water is drawn into the cylinder through a one-way valve. Then when the treadle is pushed down the water moves up through the open piston. On the next up-stroke the water is pushed out of the outlet. Very simple and straight-forward. The motion required is comfortable for someone to continue over a long period of time, and a treadle pump can typically pump about 4.5 cubic meters of water per hour. If required, the pump can also be connected to a sprinkler system to water crops.
The treadle pump can be made out of a number of different materials based on what is available locally. The actual treadle and the support frame can be made out of seemingly anything; bamboo, metal, wood, etc. This is one of the things that make it so popular. Some metal is required for the pistons and cylinders, however, because the design is so simple they can be made by a local shop if material is available. The valves are also fairly simple and can be made of old tires or rubber found elsewhere (a higher cost option is a PVC check valve). The riser can be made from either metal or PVC pipe or bamboo.
Besides the basic design there are a couple of different versions of the treadle pump:
- The River Pump – This version is designed to pump surface water. It is basically the same as all other treadle pumps except that it is built on a portable stand so that it can be moved to different surface water sources. Suction is achieved by connecting a hose to the pump and then dropping it into the water. This could be a great way to get water if you live near a river or lake, however, I am not sure how far the water can be pumped from.
- The Concrete Pump – Same as basic pump except that the cylinders are made of PVC and are encased in concrete. This version is used in areas where the water is saline (salty) and would rust metal cylinders.
The costs for a treadle pump can be anywhere from $20 to $100 depending on proximity of where the pump is bought from to where it will be installed as well as what material/type of pump is required (this does not include the cost to dig the well which the pump will sit on top of). Also, because there are not a lot of moving parts there is not a lot of maintenance that is required. If something does need to be replaced the components are simple enough that it can either be done by the owner or by a local craftsman (this is true for the simpler versions. Replacement parts for those manufactured on a large scale out of metal may be harder to get).
If funds are available there are also several organizations that either make treadle pumps themselves or who contract with local shops to make them. Three organizations doing this are KickStart, Enterprise Works and AOV International.
One limitation of the treadle pump is that it can only pump water from a depth up to seven meters, so that needs to be taken into consideration when decided on a type of pump. Another thing that I’ve read is that it’s really meant for irrigation and not for drinking water because outlet is near ground which makes it hard to collect the water from. However, I don’t see why you couldn’t get creative and attach a hose to the outlet which would make it easier to fill containers. Lastly, while it is probably a good workout, having to stand on the pump and use your legs to get the water flowing may be difficult for older people in the community, or for small children (may not have the weight/strength to move treadles), so that should be taken into consideration.
Even with these few limitations the treadle pump seems like a winner to me. It is low cost, low maintenance, easy to use, can be made of a number of different materials so you can find something locally available to make it out of, can be mobile, can be used for surface or groundwater, etc. And, as I said before, you’ll get a nice workout while you’re using it. Win-Win! Oh, and obviously it provides much needed water that can be used for irrigation, washing, or drinking. Win-Win-Win!
Moving on, the next pump I will be talking about is the Malda Hand Pump.
Malda Hand Pump
The Malda hand pump is a direct action hand pump. This means that the water is moved as a direct result of the movement made by the person using the pump. Let’s jump right in and look at how it works.
The Malda pump has a handle on top of the pump stand that moves up and down. The handle is attached to a “pumprod” that is usually made of a light material, such as PVC. This pumprod is air-tight and extends down the riser pipe. The combination of it being made of a light material and being air-tight (air-filled) reduces the force needed to raise the pumprod because it is partially buoyant . To pump water using this pump all you have to do is push the handle down and pull it up. Because the pumprod is only approximately 6-10 mm smaller in diameter than the rising main, giving little clearance between the two, it displaces more water on the down stroke then can fit in this small space. This causes water to be pumped out of the spout on the down stroke. Then, on the up stroke, the valve on the bottom of the pumprod is closed, and the user is basically pulling the water up the rising main, and then it flows out of the spout. So this pump has the advantage of water being delivered on both the up stroke and the down stroke.
As I said earlier, this pump is a little more complicated than the treadle pump, mainly because of the number of components. But once you get past that it’s actually fairly simple. The different materials required for this pump include galvanized steel, stainless steel, and PVC or HDPE which makes the pump and its components completely resistant to corrosion. These materials are also fairly readily available in most parts of the world, but it will take a skilled craftsman to make the parts. The materials will make this pump more expensive than a treadle pump, and while it can pump from a greater depth, it will actually deliver less water (see below). It should be kept in mind that in very rural areas it may take some time to get replacement parts. Maintenance is made simpler by the fact that the entire pumping element can be pulled out in one piece with simple tools.
The Malda pump is limited to a 15 meter pumping lift, but it is not recommended to go beyond 12 meters. It should be noted that while the upstroke is made easier by the buoyant pumprod, it does take some effort, and the person operating it still needs to be strong enough to raise it. As the pump goes deeper it is harder to raise because of the weight of the water. Depending on the depth of the pump it can deliver anywhere from 1.2 – 3 cubic meters of water per hour. I couldn’t find any figures on the cost of a Malda pump (if anyone knows please pass that information along), however, it is listed as a low cost option. The cost would also depend on where you are in the world and the availability of the materials.
Overall the Malda pump is a low-cost, easy to use, and easy to maintain pump. The fact that you can pull the entire pumping mechanism out in order to work on it is a huge benefit to the people using it. It is limited by the strength of the people using it, so similar to the treadle pump, it may be hard or impossible for older or very young people to use is efficiently.
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Both of the pumps talked about today are good in different situations. I’m a fan of simple technologies that use local material, and therefore, if the water is within 7 meters I would choose the treadle pump. It pumps out more water per hour, costs less (based on a non-metal model), and it is simpler which means it is easier to maintain. Also, being simple means there are less parts that can break, which means less replacement parts to try and find. Saying that, you would think that if properly manufactured the Malda pump would be able to withstand more wear and tear purely because it’s made out of steel. Is there a correct choice here? I don’t think so. It all depends on the situation that the pump will be used in. These are just two more options to be considered when making the choice of what pump works best for you. Below you will find some good resources for both pumps, including specifications, installation, and maintenance instructions.
Have you ever used or built either of these pumps? If so, how did it work out for you? I’d love to hear about your experience. Until next time, thanks for reading.