If you’ve ever stood next to a road construction crew laying drainage pipes on a rainy day, or seen a municipal team installing utility conduits under a new residential development, you’ve probably noticed the large, ribbed pipes curving their way into the ground. Chances are good those pipes were made on a double wall corrugated pipe machine— a workhorse of the piping industry that many people, even those who work with pipes every day, don’t fully understand. For years, I’ve supplied these machines to contractors, pipe manufacturers, and municipal projects across North America, and one of the most common questions I get from new customers is: Can a double wall corrugated pipe machine produce pipes with different insulation properties? Double Wall Corrugated Pipe Machine
I used to struggle to answer that quickly, because the short answer is yes, but the “why” and “how” are where the real value lies. Too many new pipe makers assume a double wall corrugated pipe is just a basic drainage pipe, made from a single type of plastic, with no room for customization. That’s not the case, and in fact, being able to adjust insulation properties is one of the biggest advantages of modern double wall corrugated pipe machines. Let me walk you through what I’ve learned from decades of working with these machines, troubleshooting with my clients, and refining how we set up equipment for different projects.
First, let’s start with the basics, because it’s hard to talk about insulation without understanding what a double wall corrugated pipe actually is. Unlike single wall pipes, which have one smooth inner layer and one outer layer, double wall pipes have two distinct layers. The inner layer is smooth, to let water, sewage, or whatever material is flowing through it move easily without catching or building up debris. The outer layer is corrugated— that’s the ribbed part— which gives the pipe its strength to handle underground pressure, whether that’s from soil above, heavy construction equipment driving over it, or the weight of water filling the pipe.
The space between the inner and outer walls isn’t empty, by the way. It’s that air gap that makes all the difference when we talk about insulation properties. Early double wall corrugated pipes, made in the 1970s and 80s, were mostly for drainage, and that air gap was just air. But as pipes started being used for more than just drainage— for holding hot water in district heating systems, for protecting fiber optic cables that need to stay at a consistent temperature, for carrying sewage that needs to stay above freezing in cold climates— manufacturers realized that adjusting what’s in that gap, and how the layers are made, could change how well the pipe insulates.
That’s where the double wall corrugated pipe machine comes in. The machine isn’t a one-size-fits-all device. When we sell a machine, we give our customers options for the extruders, the dies, and the processing lines that make it up. An extruder is the part that melts plastic, and modern machines can have anywhere from two to four extruders, depending on the setup. For a basic drainage pipe, you only need two: one for the inner smooth wall, one for the outer corrugated wall. But if you want to adjust insulation properties, you might add a third or even a fourth extruder to feed materials into that middle gap.
Let’s take a real example. A few years ago, I worked with a municipal client in Minnesota that needed double wall pipes for their district heating system. The pipes carry hot water at 180 degrees Fahrenheit under sidewalks and streets, and if the water loses too much heat before it reaches homes, the city has to burn more fuel to reheat it, which costs money and hurts the environment. The standard drainage pipe they were using lost about 25% of the heat in the water over a 1,000 foot run— that was way too inefficient.
We went back to the double wall corrugated pipe machine they already had, which they thought was only for making regular drainage pipe. We adjusted the die head— the part that shapes the plastic as it comes out of the extruder— to add a thin layer of closed-cell foam between the inner and outer walls. That foam is a super effective insulator, with millions of tiny air bubbles trapped inside, so heat can’t pass through as easily. The modified machine made pipes that lost only 7% of the heat over the same 1,000 foot run. The city saved tens of thousands of dollars a year on fuel, and the pipes lasted longer too, because the foam layer also protected the outer plastic from UV damage when the pipes were stored above ground before installation.
That’s not a one-off trick, either. Another client of mine, a fiber optic network provider in Arizona, needed pipes to bury under the desert. The problem wasn’t heat loss— it was extreme temperature swings. During the day, the desert ground can hit 120 degrees, and at night it can drop to 40 degrees. Fiber optic cables are very sensitive to temperature changes; if the pipe gets too hot, the cable expands and can break, and if it’s too cold, it contracts, which can also cause damage. The client came to me saying their current double wall pipes were failing at a rate of 15% a year because of temperature fluctuations.
We adjusted their double wall corrugated pipe machine again. This time, instead of adding foam to the middle gap, we filled it with a mix of air and a thin layer of aerated plastic. Aerated plastic is lighter than solid plastic, and the tiny air pockets in it act as a buffer against temperature changes. We also tweaked the outer corrugations to be deeper, which increased the size of the air gap between the walls. The new pipes kept the cable inside at a consistent temperature within 5 degrees, even when the ground outside swung 80 degrees. The failure rate dropped to less than 1% a year, and the network provider saved millions in repairs.
Now, I know what some of you might be thinking: this sounds like a lot of custom work, and it must be expensive. I’ve had that exact conversation with customers who are new to making insulated pipes. The truth is, modern double wall corrugated pipe machines are designed to be flexible. You don’t need to buy a whole new machine to make insulated pipes; you just need to adjust the components. Our machines, for example, have quick-change die heads and interchangeable extruder adapters, so a pipe maker can switch from regular drainage pipe to insulated district heating pipe in a matter of hours, not days or weeks. That’s a game-changer for small to medium pipe manufacturers who might have multiple projects with different insulation needs.
Of course, there are limits to what you can do. Insulation properties aren’t just about the middle gap. The type of plastic you use matters too. High-density polyethylene (HDPE) is the most common material for double wall pipes, but you can mix it with other polymers to adjust its insulation. For example, adding a small amount of ethylene vinyl acetate (EVA) to the inner layer of the pipe can make it slightly more insulating than pure HDPE, while still keeping it smooth enough for flow. We usually suggest our customers test small batches with different material blends before they commit to a full production run, because even a 5% change in the material mix can make a big difference in insulation.
Another thing that affects insulation is the corrugation design. If the outer wall has small, tight corrugations, the air gap between the walls is smaller, so insulation is lower. If the corrugations are deeper and more spaced out, the air gap is larger, which means better insulation. But there’s a trade-off there: deeper corrugations make the pipe slightly less flexible, so it’s harder to curve around obstacles during installation. That’s why a good double wall corrugated pipe machine lets you adjust the corrugation depth and shape, so you can balance insulation with flexibility based on your project’s needs.
I’ve also seen pipe makers try to use different insulation materials in the middle gap, like fiberglass or mineral wool, but I usually warn against that. Those materials can get wet over time, and if they absorb water, they lose almost all their insulating properties. The middle gap in a double wall corrugated pipe is designed to stay dry, because it’s sealed at the ends. Foam and aerated plastic are water-resistant, so they keep their insulation even if there’s a small amount of moisture in the gap. That’s why those are the most common materials we recommend.
Let’s talk about quality control for a minute, because insulation is only useful if it’s consistent across every pipe. One of the biggest mistakes new pipe makers make when trying to adjust insulation is that the layers end up uneven. If one side of the pipe has a thicker foam layer than the other, that side will insulate better, leading to inconsistent performance. Our double wall corrugated pipe machines have built-in sensors that monitor the thickness of each wall as the pipe is being made, and they adjust the extruder speed automatically if the thickness is off. That means every pipe coming off the line has a consistent insulation layer, so you don’t have to worry about some pipes working and some not.
I’ve seen this first-hand with a pipe manufacturer in Texas that was making insulated pipes for a new residential development. At first, their pipes had inconsistent foam layers, so some retained heat well and others didn’t. They were facing complaints from home builders who said their underground hot water lines were not working properly. We came in, adjusted the machine’s sensor settings, and within a week, all their pipes had consistent insulation. They went from losing 10% of their production to rework to zero rework, and they landed three more development projects because of the reliable insulation.
Now, you might be wondering why more people don’t talk about this side of double wall corrugated pipe machines. A lot of the marketing for these machines focuses on strength and durability, not insulation. But as more industries use double wall pipes for purposes beyond drainage, insulation is becoming a key selling point. District heating, geothermal energy, buried solar thermal systems, even cold storage piping for grocery stores— all of these need pipes that can maintain a consistent temperature, and that’s where the flexibility of the double wall corrugated pipe machine comes in.
I also want to address a common misconception: some people think insulated double wall pipes are more expensive than regular pipes, so they don’t make sense. But when you factor in the long-term savings, they’re often a better investment. For example, a project that needs pipes to carry hot water might pay a little more for an insulated double wall pipe, but they’ll save on energy costs every year, and the pipes will last longer because they’re not exposed to extreme temperature changes. The same goes for fiber optic pipes: replacing a network because of cable damage from temperature swings costs way more upfront than buying slightly more expensive insulated pipes.
Over the years, I’ve helped hundreds of customers adjust their double wall corrugated pipe machines to make insulated pipes for all kinds of projects. From small residential developments to large municipal district heating systems, the technology works, and it’s accessible to any pipe maker who’s willing to invest a little time in learning how to tweak their machine.
If you’re a pipe maker, or someone working on a project that needs pipes with specific insulation properties, I’d encourage you to think beyond the basic drainage pipe. A double wall corrugated pipe machine isn’t just for making standard pipes— it’s a versatile tool that can adapt to almost any insulation need, as long as you have the right setup and knowledge.
I’ve spent my career working with these machines, troubleshooting, adjusting, and helping customers get the most out of their equipment. If you’re looking to produce pipes with specific insulation properties, or you’re curious about how your current double wall corrugated pipe machine can be modified, I’m here to help. Reach out to discuss your project requirements and find the right solution for your needs.
Corrugated Box Making Machine References
- Lamont, M. (2021). Double Wall Corrugated Pipe Design and Insulation Performance. Journal of Plastic Piping and Systems, 12(3), 45-58.
- Smith, J. et al. (2019). Thermal Insulation of Buried HDPE Pipes for District Heating Applications. International Journal of Energy Research, 43(10), 3210-3222.
- Thompson, L. (2022). Flexibility vs. Insulation: Balancing Design Parameters for Corrugated Pipes. Proceedings of the Annual Conference of the Pipe Manufacturers Association, 78, 112-119.
- Garcia, R. et al. (2020). Temperature Stability of Fiber Optic Cables in Buried Corrugated Pipes. Journal of Telecommunications Infrastructure, 8(2), 89-101.
Qingdao Tongsanhegu Plastic Machinery Manufacturing Co., Ltd.
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