The Role of Steel and Polyethylene Pipes in Water Supply Systems

The Role of Steel and Polyethylene Pipes in Water Supply Systems

Kaylie: Hi, welcome, and thank you for tuning in to the AGRU America podcast. Today, we are discussing the differences in performance between steel and polyethylene piping in water supply systems.

Joining me is Cody Miles. Together, we will talk about the merits of pipes made with a PE 4710 or a superior PE 100-RC resin, and some ways the material can be used in place of steel pipes.

Welcome, Cody.

Cody: Thank you, Kaylie.

Kaylie: Today we are talking about two common piping materials used in water supply systems. First, why do you think this is an important discussion to have?

Cody: The aging water infrastructure in the United States costs millions of dollars every year in leaks alone. And modernizing these aging systems will be very costly. Therefore, I think it’s important to discuss the merits and drawbacks of different piping materials.

Kaylie: I know that piping material can affect many aspects of a water supply system, such as where and how it can be built. What are some other factors affected by the piping material?

Cody: As you mentioned, the piping material cost can make a big difference at the start of the project. But I think focusing on the material’s immediate impact on the project budget is a bit shortsighted. Piping systems are meant to be in place for decades, so how the material performs through the years is equally as important, in my opinion.

Kaylie: Right, so what is one long-term factor that you would consider paramount to a successful water supply system. 

Cody: There are many, but I’d start with something basic like flow capacity.

Kaylie: Interesting. Pipes are shipped and installed with all project stakeholders well aware of the expected flow capacity of their system. 

Cody: That’s true, but as you know some piping materials can have their flow capacity decrease over time.

Kaylie: Sounds like you are talking about buildup within the pipe itself.

Cody: Exactly. Most pipe materials have to deal with biological growth, pitting, rust, and corrosion. These processes will go on to affect the pipe’s roughness coefficient. In time, the water flow velocity will be impacted, requiring more energy to pump the same volume of water.

Kaylie: From what I understand, corrosion seems to be the main drawback of most piping materials. Corrosion can lead to pitting and buildup within the pipe, affecting flow capacity.

Cody: That’s true. Steel pipes, for example, must be coated to help control corrosion. Other methods are also implemented, but these are just temporary solutions that help limit corrosion—not prevent it. And I think this area is where you will see the benefits of polyethylene piping really shine.

Kaylie: I know that polyethylene is not affected by corrosion. Does that mean its roughness coefficient will remain unchanged throughout the duration of a project?

Cody: Yeah, while other materials like cast iron and steel pipes can have their roughness coefficient drop by more than half in a 50-year span, polyethylene’s roughness coefficient stays the same thanks to its chemical resistance.

Kaylie: So, with a polyethylene piping system you have a smooth internal wall with uninterrupted water flow.

Cody: Right, and uninterrupted water flow means a predictable amount of energy every year to pump the water through the system.

Kaylie: I know we talked a lot about leakage rates in the past and how the United States ranks compared with the rest of the world. Just how bad is it?

Cody: Our leakage rates vary from State to State, but overall, we are fortunately not at the 40% range you see in some countries. But even our average leakage rate represents about 6 billion gallons of water lost every day.

Kaylie: That’s an unsustainable amount of treated water to lose.

Cody: It’s hard to fathom, for sure. And while pipe joints aren’t the only source of leaks in a water supply system, they are an addressable problem.

Kaylie: For most materials, there is an acceptable leakage rate that is factored into each installed joint, right?

Cody: It depends on the joint and materials being used. In this regard, steel and polyethylene are similar; both have pipes and fittings that can be welded together to create leak-free joints.

Kaylie: You mention leak-proof joint several times. I’d like to clarify how this is possible. Different segments of pipes are brought together at joints using pipe fittings.  With some systems, these joints are often a source of leaks. For polyethylene pipes, on the other hand, there is the option of fusion welding the pipe and pipe fittings together. The resulting fusion welded joint is leak free and will positively impact the system on multiple fronts.

Cody: That’s right. If you are able to address exfiltration from a water supply system at the joints, then you are not only addressing water loss, but also reducing the frequency of maintenance.

Kaylie: I know in some applications, downtime as a result of maintenance can be detrimental. Nuclear power plants, for example. PE 4710 and PE 100-RC resin pipes are generally favored in the water supply systems built to support nuclear power plants due to their long-term reliability. And by building a robust system that does not have high maintenance requirements, power plants can save millions and dramatically improve site safety.

Cody: I like that you brought up safety. The durability of polyethylene pipes has improved thanks to improving resin grades. Today’s PE 4710 allows for larger pipes than what was possible several decades ago. And recently, enhanced resins like PE 100-RC are available, which supports the creation of large diameter pipes for projects requiring high-capacity flow.

Kaylie: Yeah, AGRU’s  XXL piping system has been used to create outfall pipes for a number of wastewater treatment facilities in North America and have been incorporated in stormwater systems abroad. But these large pipes, reaching 3.5 m in diameter, can be used anywhere large volume flow is required such as in power plants or desalination facilities.

Cody: Would you say PE 100-RC is an improvement over PE 4710?

Kaylie: In terms of strength and stress crack resistance, both factors that are essential for creating pipes at these larger diameters, then yes. But that’s not to say PE 4710 isn’t already a very good piping material.

In a previous blog, we discussed a report by the Water Research Foundation. In that report, they cited the Kobe earthquake in Japan during the 90s and found that out of all the piping materials used, the polyethylene pipes were the only ones that did not sustain any damage. Steel was the second best, with about .26 failures per mile.

That report does go on to mention that larger diameter pipes tend to outperform smaller diameter pipes.

Cody: So, what I am hearing is that if you want the top-of-the-line piping system in a seismic zone, go with AGRU’s XXL piping system made with PE 100-RC for resiliency, the longest life expectancy with low maintenance?

Kaylie: Not every application requires such a large flow capacity, but I hope it is clear from our discussion today that pipes made with PE 100-RC offer an excellent balance of strength, durability, and long-term sustainability—the trifecta of a cost-effective water supply system.

And with that, our podcast has come to an end. Thanks again for joining me today, Cody. To our listeners, thank you for tuning in. We hope you’ve enjoyed this podcast. For more information about AGRU polyethylene pipes, fittings, and other solutions, please visit us on the web at AGRU America dot COM.