Andrew and others,

Thanks for the compliment, I'm mostly happy about the way the pump worked out.

Everything was 4-inch in size, the piston, valves, and tubing. Anything smaller and I'm concerned it won't pass the hard trash, anything larger and I'm concerned the inlet tube won't fit into the squatting hole.

If I were to do it again, I'd make the piston 3-inch, since pumping up from 1 meter gets rather hard, even if you are only doing it for a few minutes. Probably no further mechanical advantage would be needed.

The valves are available at pvcpipesupplies.com, and they come in a variety of sizes, clear and white body, threaded body or socket body. The 4-inch plastic hose barbs were not easy to find either, they are from www.spears.com.

As for grit wearing the cylinder, it would seem that simply replacing the pipe would be an option. I've not seen that issue, though my pump hasn't seen all that much usage.

As for future plans, I think it will take more time, effort, and resources than I have to develop this pump to a point where it's really ready to use. What I'd like to do is pass it off to people who have those resources. Of course I'm always happy to share what I've learned.

Dale

Hi Dale,

Thanks for posting. What size pipe are you using for the cylinder and up to the valves? Can you provide manufacturer information about the valves? I'm looking forward to hearing more about the pump as testing continues. Do you have a test plan/strategy?

The next issue I need to resolve with my pump is the durability of the cylinder. It gets scored by grit and then begins to leak.

Sanergy had one of my earlier pumps. If they still have it if it is still around and they don't want it, you are welcome to it. It might be nice to add some mechanical leverage to your pump.

You are making headway - good job.

Cheers,

Andrew

I've been writing about manual sludge pumps with clog resistant valves, and have now built and field tested a pump. It was tested in Nairobi in August, 2019, mostly under easy conditions, but it worked well.

The idea is to use the basic arrangement of a piston and 2 one-way valves, but to use valves that resist clogging. In tests at home, rags, bags, bottles, cans, shirts, and various other bits of trash passed through the pump successfully. Pumping rates of 90 liters per minute and probably more are achievable under easy conditions.

I'll attach a few still photos, but the youtube video is really the thing to see. One still photo includes some of the trash that has passed through the pump. Other still photos shows some of the parts of the pump, and an overall view of a non-quite-final version of the pump.

The video is at:



The pump works well in thin sludge with low lift. It can work well in slightly thick sludge, as seen in the video. It can work well with 1 meter lift once the pump is primed (that is, has liquid in the valves). I'll point out that pit latrines are rarely emptied unless they are full, so the start of the pump priming is always at low lift.

This design is a work in progress. I've made a good start, I think, but to really develop this pump requires someone with more time and resources than I have available.

Contact me for more information.

Dale Andreatta, Ph.D., P. E.
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Hi Dale,

Another option, while a bit more complicated, is a pinch valve. I think it would need to be custom made though and the tooling won't be cheap.

AW

Andrew and all,

It's good to see that others are thinking of handpumps and the valves that are required. (As an aside, there are ways to build pumps with either one valve or no valves, but I think such pumps would be cumbersome to use.)

I've been working with 1-sided flapper valves in 4-inch size for a few months now. They seem to work well, pumping thin or reasonably thick simulated sludge, and passing bottles, cans, bags, and rags. I'm still finalizing the design, but in the next month or so I'll post some video, then I expect I'll go to Africa in the latter part of 2019 for field work. My work is all self funded, so I don't have time for major testing, but I'll at least do small scale testing. That is, unless I could find the right partner...…….

I have some 3-inch duckbill valves that were not too expensive, but since my flapper valves are working well and you recommend them so poorly, I doubt that I'll even bother to try them. Possibly a custom duckbill valve, that could have advantages.

Stay tuned in about a month for video and more details,

Dale Andreatta
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Hi Dale,

Regarding valves suitable for liquid-waste pumps: I tested a wide variety of valves during the development of my pump. Duckbill valves did not work well and large ones tend to be expensive. Perhaps a custom duckbill valve that is less flow-restricting would work (more on that in a moment). Flapper valves and ball-float valves were fouled too easily.

I am nearly done with the development of a custom valve that requires little force to activate, opens and closes quickly for high efficiency, is reliable (the first prototype survived over 240,000 cycles before ending the test), and will be very easy to access and clear or exchange. The only hurdle to face now is funding the prototype and testing. I don't foresee that happening soon but will let you know if I achieve the desired results.

Cheers,

AW

Regarding screening the trash, if you put the trash screen at the inlet then the trash just accumulates in the pit and must eventually be dealt with. If you put the trash screen above ground but before the valves, as with the Beaumont Sludge Pump, then you must open the system frequently to take the trash away from the screen. The Beaumont pump has a mechanism for doing this without too much effort, but it still takes some time .

I believe we can and should do better. One could see trash in the pit as an opportunity to provide sanitation service and municipal trash collection at the same time. Everywhere I've been in the developing world the trash accumulates, creating a trash nuisance, until someone sets fire to it, creating a smoke nuisance.

Bucket-based manual methods exist for handling the trash and sludge together. My Sludge Digger and Sludge Dipper designs do this. The Dipper is for thin sludge only and the Digger handles thick or thin sludge. See:



For taking the trash only out of the pit, there is the crabtrap, mostly designed by some students that I worked with a couple years ago:



None of these are as neat and tidy or as fast as a sludge pump or a vacuum truck, hence I believe we need a sludge pump with valves than can handle trash.

Dale Andreatta

Hi Dale,
It is interesting to see that regardless of what country you are in, people keep throwing trash into their septic/sewage systems.

The best advice I could give is a coarse screen before the valve that might stop stuff getting stuck in the valve and make it easier to clean.
Also, as an operational routine, moving the pump frequently may allow trash that is getting pulled towards the pump to move away.

A slightly larger neoprene tricuspid joker valve (commercial sizes are commonly only 1" or 1 1/2") would probably work well. But I doubt they could be made in a DIY fashion.

For the single sided valves, look for "scupper valves". For hand-pumps a common version is made from a leather flap. But I am not sure those would work well for sludge with solids.

There seem to be 3 types of sludge pumps out there, the Gulper, the Rammer (also known as Gulper 2.0) and the Beaumont Sludge Pump. All of them seem to have valves that are easily clogged with trash. The photos I've attached are from a day in Malawi, with me operating the Gulper, the clogged Gulper getting fixed, the trash that come out of the Gulper, and a close up of the valves of a clean Gulper. The Gulper worked really well until it clogged.

Various methods have been tried to screen the trash before it hits the valves. It would seem that this may or may not work, and in any case is only a partial solution.



I am starting a project to build a sludge pump with valves that are less likely to clog. What I would like to know is, has anyone tried other types of valves, and how did they work.

I'm looking at two types of possible valves. One is a flexible check valve made of rubber, sometimes called a duckbill valve due to its shape. Commercial valves are very expensive, it may be possible to make a home-made version. The other valve is a single sided flapper valve similar to what is in the bottom of a flush toilet tank. These are cheap, but hard to fit in a small space. Using either type of valve is not an easy task, so there is no promise that this will work. I hope to have something working by the time of FSM5, and to do some field testing while in Africa.

Thanks,

Dale Andreatta, Ph.D., PE
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