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Tired of Rusting, Leaking Pipes? from Aquatherm, Inc.

Facility Managers and Pre-emptive Maintenance

By Steve Clark, PE, CEM

In international relations, the doctrine of pre-emptive first strike is controversial, so I won’t go there.

However, in facility maintenance, pre-emptive maintenance is a common sense best practice that forward-looking FM Engineers practice.

A conversation I had with an FM engineer at a large state university prompted this article.   We were discussing the specification of products that would save the school maintenance costs, when he told me that he had no input on those decisions.  He explained that when a building was complete, he would get a walk through with the contractor and whatever was there, it was now his job to maintain.    Ouch.    Depressing news at best.    An expensive and wasteful practice at worse.   


In contrast, it was fascinating to watch the process followed by the FM staff at the King County (Seattle, Washington) prison system.   First, they were fully aware of one of their largest ongoing maintenance costs: failing pressure pipes.   They did their homework.   What was the source of the problem?  That the basic materials used in their piping systems were easily attacked by the aggressive supply water in the region.   They thoroughly researched piping materials and joining systems.  They met with manufacturers.  And in the end, they did what might appear to be radical: They specified polypropylene-random (PP-R) for their pressure pipes.  

Hospitals, universities, schools, military bases and industrial plants across the U.S. are doing the same thing.  The driving factor on these projects was the need for a long-term, reliable system. Most of them have learned the same thing that Terry C. Smith, VP of Engineering at Marriott International, told me, “Leaky pressure pipes are our number one maintenance expense.”


Polypropylene Pressure Pipe

While polypropylene has been virtually ignored for potable and pressure pipe applications in North America until the last few years, many plumbing engineers are familiar with its benefits. Acid waste pipe often is made from polypropylene due to its extremely high resistance to most chemicals. The long chains of polymers do not provide a weak point for chemicals to attack. Also, PP often is used in deionized, or ultra-pure, water systems.

Why the sudden adoption of polypropylene into potable and hydronic applications by such venerable and conservative engineering organizations as the Army Corp of Engineers? This article explores five factors that have contributed to this change in the market. Three factors have to do with advances in PP technology, one factor involves the green movement in general, and last but not least, many of the North American Plumbing Codes have finally been updated to recognize polypropylene as a safe and effective piping system.



Development of High-Temperature and High-Pressure Polypropylene

Basic polypropylene has many features that make it a suitable piping material. It is resistant to corrosion and abrasion, and it does not support scale formation. However, for use in hot, pressurized fluid systems, it has two serious limitations:

  1. The temperature and pressure rating is not high enough for boiler or domestic hot water heating applications.
  2. The thermal expansion is excessive.

The physical strength of polypropylene pipe is affected by the polymers’ chain lengths. PP-H (long polymer chains) is a tough material that can be inflexible and brittle. PP-S (short polymer chains) has short chains resulting in a more flexible pipe that is not as strong. A blending of short and long polymer chains called PP-R) offers the best of both worlds, resulting in a tough, yet flexible, material. With the addition of trace amounts of the right property-enhancing compounds, the performance of PP-R is increased further. The result is a PP-R piping system that has twice the pressure rating of standard PP. This engineered piping material can handle 180°F boiler water at 100 pounds per square inch (psi) for 50 years.


Control of Thermal Expansion

For decades, the natural linear expansion rate of plastic pipe was a major source of frustration for piping engineers. Its growth rate of 10 inches per 100 feet per 100°F was simply more than anyone could live with.

German engineering solved this problem. The PP-R pipe is extruded in three layers, and the middle layer contains small pieces of a fiber product running longitudinally with the run of the pipe (see Figure 1). These pieces restrict the thermal expansion of the pipe by 75% and bring it to the same order of magnitude as metal pipe. 


Figure 1. The small pieces of a fiber material running longitudinally with the run of the three-layered PP-R pipe are highlighted in the circle. These fibers reduce thermal expansion by 75%.


Development of Socket Fusion Connection Technology

Historically, the weak link in piping systems exists at the connection. Mankind has experimented with dozens of methods to connect pipes and fittings, with varying degrees of failure. Methods that use a foreign material, like glues, solders, gaskets, or pipe tape, increase the possible number of failure modes. Mechanical fasteners can come loose. Chemical bonds require a degree of chemical sensitivity that can result in failures. Welding can make a great connection that is as strong as the pipe itself, when done properly by skilled craftsmen.

Socket fusion offers this level of connection without being as labor intensive. The procedure is as follows (see Figure 2):

  1. Insert pipe and fitting onto the welding device.
  2. Heat pipe and fitting for the specified time.
  3. Gently join pipe and fitting for a lifetime connection in seconds.

Figure 2.  Socket fusion procedure.


Heat fusion connections are simple, quick, and reliable. By forming a connection that has the same physical properties as the pipe and fitting, systematic weaknesses are eliminated. Eliminating the addition of foreign materials (such as gaskets and glues) to the piping system reduces the potential of chemical or mechanical failures.  Socket fusion also prevents catastrophic blow outs at the joints, which are common in other socket or mechanical type connections. The result is a connection without a potential leak path or failure mode.  The connections are the strongest part of the piping system instead of the weakest link.


Figure 3. Once fused, the fitting and pipe become one piece with no leak path or weak point.

Proper fusion connections won’t leak or fail over time, so maintenance or repair concerns are alleviated.



In the past, we typically accepted that the products we purchased were engineered to fail.  We called this “planned obsolescence.” In five or 10 years, we would throw it away and buy a new one. This way of thinking now looks foolish on a number of levels, but it is particularly crazy for piping systems. When pipe systems fail, they can cause extensive damage, and replacing a failed pipe costs far more than the cost of the pipe. Thus, buildings and the pipes in them need to last for 50 years, not 15. According to Mike Dodson, Director of Engineering for Virginia Mason Medical Center in Seattle, copper pipes in the Pacific Northwest are now failing in as little as five to seven years. When pipes fail they often damage many other building systems, and the replacement of piping systems often impacts other components of a structure.  The environmental impact of replacing a failed piping system before the building needs to be replaced is substantial.

                The first leak is rarely the last leak. A piping system that is leaking has failed and becomes an ongoing expense for building management. So choosing a piping system that will outlast the building should be the driving factor in specifying a green piping system. 

                Another environmental advantage of polypropylene is that it is made of just carbon and hydrogen and contains no toxins, PVCs or heavy metals.  PP can be recycled, and the manufacturing process has a low carbon footprint.


Code Acceptance


As little as six years ago, none of the North American plumbing codes recognized PP-R as an accepted material for plumbing.  In that time PP-R has been added or is being added to most modern codes.  Even in areas in which the code has not been updated, the authority having jurisdiction typically approves its use after evaluating the considerable evidence of its worldwide safe track record. 




Being a facility engineer means being an expert on pipes. As such, you are obligated to yourself and your facility to learn all you can about every piping system that could benefit the projects you maintain and design.  Polypropylene is a viable solution for some of the challenges you face and deserves to be added to your arsenal of engineering answers.


Aquatherm Greenpipe® is a recyclable polypropylene piping system designed specifically for potable water applications and proven around the world for 30-plus years. A heat fusion connection eliminates toxic materials and open flames from piping installations and results in a homogeneous material, eliminating systematic weaknesses and leakage paths. Aquatherm’s Greenpipe, Climatherm (HVAC) and Lilac (reclaimed water) come in pipe dimensions ranging from 3/8" to 12" (equivalent) and possess extensive code approvals.