Thermoforming 2, The Coral Sea Edition

 In this post I'll be describing how to thermoform HDPE pipe, a technique that I think anyone doing water and sanitation work in Vanuatu might find useful. Before getting to the technical details though, I want to talk about the local context for this kind of work and I'll include a bunch of my favorite photos so it may be worth browsing through this long post even if you don't see yourself ever doing any thermoforming at home.

 Vanuatu might not be classified as a “developed” country in terms of having large industrial and service sectors or boasting a high GDP. Nonetheless, you do see a shiny veneer of modernity at the country's resorts and around the capital city. But if you make your way to an outer island like Maewo you may find yourself among people who do actually seem to be, to a large extent at least, disconnected from the modern industrialized world. I got to thinking about that while sitting in my host family's yard, a compound of houses that is home to about fifteen people.

  Looking around, I started counting on my fingers the things that someone had brought to the island by ship or plane from the outside world. Aside from the store-bought clothing and ubiquitous knives of all sizes, I hardly ran out of fingers--on my first hand. You'd think this striking scarcity of consumer goods would make one appreciate one's own access to the "finer things in life", but what really bowls me over is an appreciation for how these Ni-vans and their culture survive and thrive on this island without having all that much in the way of those “things.” 

  I hope this doesn't sound like I'm romanticizing Ni-Vans for doing without. The things that never fail to impress me are all the things they do instead.

   Like my host mom roasting grated yam from the garden inside pieces of bamboo to cite just one delicious example.

Or how about that sweet little wheelbarrow my host brother is sitting on at the top of this post. Can you guess what they came up with to "reinvent the wheel?" (See the end of the post for the answer.)

Around here a family can build their house, from foundation to roof, with literally no imported materials. 

Granted, nowadays almost everyone will at least use some nails and maybe some door hinges and such, but when the village recently completed the three-year project of building their nakamal (KNOCK-uh-mall), the massive community lodge and gathering place that doubles as a community cyclone shelter, they had built the entire thing without using any of those things.

 This is a strictly "custom nakamal" built in traditional style using specialized skills developed over generations and with building materials available exclusively in the surrounding forest: hand hewn logs, soft and hard bamboo, natangura leaf for the roof, and an assortment of vines and fibers that hold everything together.

When I was new to Maewo, almost everyone in the village would turn out for the nakamal work days held every Friday. It was a made-to-order opportunity for me to get to know everyone and see how community projects are organized out here. Just as importantly, it helped me get a feel for the cultural approach to building things and the brilliant implementation of  traditional knowledge and skills in an elegant display of home-grown  "appropriate technology." 

I readily admit I've never completely gotten the hang of many of the skills that everyone else made look easy, like preparing the natangura leaf and then stitching it onto slats of bamboo to make the roof panels...

 ...or peeling apart vines to separate the fibrous "rope" that is used to lash those panels of roof thatch to the bamboo framing.

It really didn't matter though. There were plenty of ways for everyone to contribute to the community effort and it was always tremendous fun.

Unexpectedly, the work had to be suspended for six months when our village along with communities all over Maewo took in the evacuees from the disastrous volcanic eruptions on the neighboring island of Ambae. (Post) The half-finished nakamal was quickly converted to temporary housing and the community's focus turned to coping with the crisis that saw our village population nearly double with the arrival of the Ambaens. Eventually the rumbling over on Ambae died down, and despite the volcano still posing a "code yellow" threat, most of the evacuees were determined to pack up their belongings and made their way back across to Ambae and the work on the nakamal resumed.

By the time the nakamal was finally nearing completion we had already successfully finished our work on the main pipeline to the village and there was plenty of water available to provide the nakamal with its own tapstand. That would be a clutch amenity for the central function of any custom nakamal: the ceremonial drinking of kava.

The kava is harvested from gardens up in the hills and carried down fresh to the nakamal where the roots are trimmed and divided into individual portions. You have to throughly wash your portion to get all traces of soil out before  beginning the semi-ritualized process of hand-grinding the kava to a pulp using the special coral stone called a kwasis.

So yes, providing running water right at the nakamal seemed like a particularly apt way to celebrate the twin accomplishments of completing the nakamal and rehabbing the community water system.

Building the tapstand and piping freshwater to it would be straightforward enough. The challenge was going to be how to deal with the gallons and gallons of wastewater since the nakamal is situated just uphill from a cluster of homes. Installing a public tapstand without a really solid plan for where all the wastewater will go is a classic example of short-sightedness in development work, but nevertheless, examples abound, like this fetid, man-made bog behind the public tapstand of a nearby village, presenting both an eyesore and a public health threat.

My host Dad, Meltus, is the "Custom Chief" of the village and in his low-key way,  he had been the driving force in the completion of the multi-year project.

  Meltus came up with the idea of making a drain line using the abandoned poly pipe that we had replaced with larger pipe when we upgraded the community water system. However, when they dragged the forty-meter-long pipe down to the nakamal, it became clear that it wasn't going to be so simple. The pipe had looked straight enough when it was stretched out through the bush, but once it was pulled out of there, the pipe's "memory" kicked in and it wanted to spiral slightly this way and that, trying to return to the coiled shape of its birth. We only had a little slope to work with so if the pipe wouldn't lay flat it was never going to work as a drain. 

We decided to go with my idea which was to cut the pipe into seven-foot sections. That way, although each of the pieces would have a slight “bow,” each piece could be turned slightly so the bow would run flat along the ground. To fit the pieces together we would just need to have a socket on the upstream end of each piece of pipe. And that is where thermoforming finally comes in.

Thermoforming a socket on a pipe involves heating the end of the pipe until it is just soft enough to push it onto another piece of the same-size pipe. This stretches the heated pipe into a bell shape that becomes permanent once the pipe cools down. I described thermoforming rigid PVC pipe in this post from Panama, where I'd learned the technique from a Volunteer who'd picked it up from local tradesmen while serving in Ghana. Here in the South Pacific though, PVC pipe is never used for pipelines and is not readily available, even in the capital. In Vanuatu pipelines are all made with HDPE, which I'll refer to as poly.  The flexible poly pipe is a completely different beast from rigid PVC, but I found that you can apply the same basic techniques of thermoforming, though it requires a few tweaks along the learning curve. 

Just as I'd done in Panama we heated the end of the pipe by dunking it into a can of cooking oil heated almost to a simmer over a fire. Judging when the pipe is just soft enough but not too soft is quite tricky—it's a small window—much smaller than with PVC, but I'll have more on the technique later.

You might guess how relieved I was when everything went together as planned and now, even with the tap running full blast, the drain carries the wastewater past the nearby homes and onto a bushy slope where it can run off harmlessly. The home-made joints fit together very tightly even though, unlike for PVC, there isn't any sort of glue for use with poly pipe. Normally, the only way to join pipes together is to use these special compression fittings.

You can only get these fittings on the two big islands in Vanuatu and they're not cheap. The price tag on this one at a hardware store in Santo translates to about $20 US. These are the same couplings we used to join the big rolls of new pipe we installed for the mainline upgrade and they make excellent fittings for a high pressure pipeline.

But even if they were free, these fitting wouldn't be any good at all for drain pipes because of the way they sharply narrow the pipe at the joint, creating a constriction that would catch crud and clog up in no time.

Fortunately the home-made sockets are tight enough that the joints in the drain line (which is not under any pressure) don't leak at all. If you install each pipe with the socket facing upstream there's no "shoulder" for catching crud. Still, there will eventually be clogs but that's where assembling the pipe in seven-foot sections pays off again. When a clog happens (as it already has) it's easy enough to go along the line thumping the full pipe to figure out where the water is backing up. The joints on either side of the clog can then be pulled apart and snaked out with a stick of bamboo and the whole thing reassembled in a matter of minutes.

Because the pipe runs through a high-traffic area, we decided to secure the the joints to keep them from being accidentally kicked open. We did that by drilling a hole in the joint, going through the top of both pipes, and then using a short, stout nail to pin the joint together. I'll bet you're thinking we should have buried the pipe, and, we could, but, believe it or not, no one, including me, ever even suggested it.

This thick-walled, 50 mm poly pipe is plenty tough enough to be left exposed (HDPE doesn't break down in sunlight the way that PVC does), and the truth is, having a pipe running along the ground doesn't violate the rustic aesthetic of this neighborhood in the least. And very importantly, leaving the pipe exposed and accessible is probably the only realistic way to get the drain working again when the inevitable clogs occur.

The nakamal drain project worked out well and seems to check most of the boxes for sustainability, but it was something of a one-off. It only made sense because we had all that salvaged pipe that we didn't have a use for in the water supply system. But purchasing new 50 mm poly pipe for a drain line wouldn't ever make sense—it's way too expensive and it's not even all that well-suited to drain lines.

 The real potential for applying thermoforming is with narrower gauge poly pipe. We've discovered that the smaller pipe is an ideal material for making a smaller capacity drain--like for a kitchen sink. But you have to know how to thermoform.

It's hard to overstate what a game-changer it is for a family to have running water right inside the kitchen. More than just a convenience, a kitchen sink with running water is a crucial element for promoting family health through improved hygiene. 

In a companion post I'll describe in detail how we've been making these stylish vessel-style sinks using ferrocement. The cast-in tail piece and the drain lines are made by thermoforming 32 mm poly pipe, a size that is much cheaper if you were to purchase it new and there are random lengths of salvaged second-hand pipe here and there around the village. Even pipe that is too degraded to trust in the pressurized water supply system will work fine as a drain. The smaller pipe is also much easier to thermoform. 

Since it is fairly simple to make a sockets that can be taken on and off easily but will virtually never leak, it makes sense to assemble the drain line as a series of smaller segments of pipe, some with a bend in the middle. That way you can customize the drain line to run from the bottom of the sink to a convenient spot to exit the house and then route it to where you want to dispose of the water. You can use as many smaller sections as you need.

Here are some details about the process.

Because poly pipe is somewhat flexible, it doesn't hold it's shape well enough to work as a mold when you try to push a heat-softened pipe over it. What I found does work well is a rigid mold made by filling a short length of pipe with a strong mix of sand-cement mortar.

When the mortar has hardened, you should taper the end of the mold by shaving it with a knife. This kind of tapered mold provides two really important benefits. First, it makes it a little easier to get the mold to slide inside the mouth of the heated pipe, which is the tricky part. Then, when the pipe cools down and stiffens around the mold, the resulting socket is itself tapered, so that when you join it to another pipe, the connection gets tighter as you push it home. 

Any kind of cooking oil works and you can use the same oil over and over. You have to store it securely though because all kinds of pests will be attracted to your thermoforming oil. 

It takes practice to judge when the pipe has gotten just soft enough and more practice to get the feel for sliding it onto the mold. Plan on some early flops where you'll have to cut off the squashed end of the pipe and start over. The temperature of the oil and the thickness of the pipe wall will determine how many seconds you need to leave the pipe in the oil. 

Only submerge the pipe as deep as you want the socket to be and keep it consistently at that depth. (It helps to mark the pipe). Lift the pipe out every few seconds and use the mold to push in sideways on the end of the pipe to see if it's getting soft. When the heated pipe deflects just a little, it's about ready.

It should require a slight twisting back and forth and a solid push to get the mold to start into the heated pipe so don't give up too quickly. Once it starts inside use the back-and-forth twisting motion as you push it to the full depth. Be careful not to twist too hard or you can crinkle up the pipe. If you can't get the mold to go inside the pipe you can reheat it and try again, but don't over-soften it. It has to be a very tight fit in order to work. If the end of the pipe gets squishy and bent out of shape you just have to cut off that section and start over. Like I said, it takes practice.

If you're making several sockets you can drop the pipe with the mold still inside into a bucket of water to cool it down more quickly. Otherwise you can just leave it to cool slowly. Either way, don't take the mold out of the pipe until everything has completely cooled. If it's a good socket it will be very tight and somewhat difficult to twist the mold out.

These home-made sockets combined with home-made bends to give you complete flexibility in routing the drain line. You can make a bend by carefully heating the pipe over a fire, or better over a bed of hot coals. We found that the softened pipe tends to collapse and kink when you try to bend it unless you support the pipe from the inside by filling it with sand before heating it.

Heat the pipe evenly at the bending point by holding it over the heat and steadily rolling it until you sense the right amount of flexibility. Then lay the pipe on a flat surface where you've partially driven some nails to create a jig for the desired angle of the bend. Secure one end between two nails and then slowly bend the pipe around some kind of bending post, (a plastic peanut butter jar with its lid screwed down to the table does nicely). As you bend the pipe, use your thumbs to press down on the pipe where it's bending to discourage it from kinking. When it cools down, the pipe will want to partially spring back, so you'll want to bend it past your desired angle by ten or fifteen degrees. Use another nail to hold the pipe in position and let it cool down completely before taking it off of the jig and emptying the sand.

There's no need for anything like a P-trap under the sink since a trap is only needed when a drain connects to a septic system or sewer where putrid gases would come up back up the pipe and into the house. In our context, these “greywater” drains can often be safely emptied directly into the environment. At many of the houses around here the pipe can be routed downhill a short distance to spill out in a bushy, out-of-the-way space where the wastewater will soak away harmlessly. Any significant food particles will decompose quickly once picked over by the ubiquitous chickens and such. If there's no slope to move the water away from the house, one option is to pipe the wastewater to a shallow circular basin that you dig nearby and plant a small clump of banana trees or something similar there.

A more elaborate way to dispose of wastewater is to drain the sink into a soak pit, which is a just a hole in the ground filled with large, irregular stones and then topped off with gravel and with a layer of plastic or a cap of cement to try to keep rain out the pit. Because soak pits are designed to isolate wastewater under the ground while it is soaking in, they are widely promoted as best practice for public tapstands in village settings. We made a small one for my kitchen sink and it works fine, but I've concluded that in the context of our village, digging a soak pit to drain a single family's kitchen sink may be overkill. Soak pits have a limited lifespan at best, and there are several ways they can fail in very short order, leaving the homeowner to improvise or abandon the drain altogether. As always in infrastructure projects I think it is paramount to have a good answer to the question, “What's going to happen when this stops working?” And any time a project involves running water, the question, “Where's all the wastewater going to go?” should never be left as an afterthought. Factors to consider in planning the system include foot-traffic patterns, percolation rate of the soil, and the consequences of the ground being saturated during rainy season.

As I mentioned earlier, poly pipe can't be glued together to form a pressure-tight joint, so clearly it wouldn't be advisable to try to use thermoformed sockets to join big pipes in a pressurized system like this one in our pipeline. 

One exception to that rule though would be in a very low-pressure system such as a pipeline that captures water from a spring that is just barely uphill from the water users. 

Some families living outside of the main village have small, informal systems like that. Often they have been scrapped together using second-hand pipe that they keep held together (barely) by pieces of bamboo or some other improvised connectors.

As a stop-gap measure, a well-made coupling made of thermoformed pipe can mean the difference between people getting water at their faucet or not. 

I hesitate to say it, but if you tie these joints with a tightly wrapped strip of inner-tube rubber (a standard plumbing practice here) it probably won't leak and will likely never get replaced with a store-bought fitting. 

Even in a high pressure system a thermoformed coupling might work as a temporary patch for a broken pipe and allow you to keep the system working until a fitting can be purchased. Keep in mind that to get to that hardware store over on Santo you have to either fly over there and back on the twice-weekly flights (about $90 US each way), or take the cheaper option of hitching a ride on one of the passing cargo ships that periodically ply this part of the archipelago, but making the round trip that way will literally take weeks.

Ideally of course, village water committees will maintain an inventory of the fittings needed to make permanent, professional repairs. But in the case that they haven't, the alternative for the community won't be to do without. It will be to once again look around at what they've got to work with and figure out what they can do instead, and thermoforming is another useful tool for their toolbox.

There's more about thermoforming HDPE pipe in two companion posts, but for now I'll close with two more photos and the answer to the wheelbarrow riddle I posed at the beginning.

Among the most useful "natural" resources that people on Maewo are blessed with is the assortment of junk that breaks away from commercial fishing boats and washes ashore over on "Big-Sea" side of the island. 

A torn net is prized for repurposing as a hammock, and as my nephew and nieces can attest, a float from one of those nets makes the perfect wheel for a wheelbarrow.