PVC vs. HDPE Fittings in Underground Construction

Sewer system operators and consulting engineers from around the United States surveyed showed that HDPE and PVC finished either #1 or #2 in most categories (1). Both types of pipe have their strengths and weaknesses and appeal to many contractors and project owners due to their expansive reach in applications. The choice of pipe material will often dictate the choice of fittings that will be used in a given project. However, there are applications and situations that can take better advantage of HDPE fittings.

Below, we examine the differences between polyvinyl chloride (PVC) and high-density polyethylene (HDPE) pipes, describe applications that are ideal for HDPE fittings, and review the benefits of sourcing most HDPE pipe and fittings from the same material.

How do you compare PVC with HDPE?

When comparing PVC with HDPE it is first important to recognize that both materials demonstrate many advantages over other, more traditional piping options made with concrete, iron, steel, or copper. Most municipalities once depended on traditional piping materials for constructing water infrastructure, but that has changed as alternatives became available. Traditional piping materials have also been associated with problems that stem from leaky pipe joints, damage to the pipe due to corrosion, and general wear and tear.    

Thermoplastics like PVC and HDPE, on the other hand, offer significantly higher service life when compared with traditional piping materials. They are also less dense and therefore lighter and cheaper to transport. PVC and HDPE also demonstrate high tensile strength and are highly resistant to electrochemical-based corrosion. While both thermoplastics show many similarities, there are some key differences.

PVC has been described as a stiffer and stronger material, which carries positives as well as drawbacks. A key positive is that less PVC material is needed than HDPE to create pressure pipes at the target pressure levels. Because of its stiffness and strength, PVC can connect directly to mechanical valves, non-plastic fittings, and many types of connections. However, its lack of flexibility means that PVC requires a longer bending radii than HDPE pipes. 

HDPE is known for its high strength-to-density ratio, flexibility, and chemical stability making a strong choice for both pressure and non-pressure piping applications. While it does require more material to achieve the same pressure rating as a PVC pipe, HDPE offers a distinct advantage in having several means of achieving a leak-free system via heat fusion joints and through the use of specialized fittings.

The advantages of HDPE fittings and connections

One of the biggest problems with mechanically joined traditional pipes is the high incidence of background leakage—water that leaks out of the pipe through pipe joints. It is estimated that in the United States, about 14% of drinking water is lost each day due to background leakage, which represents more than 12 million gallons of water a year in a city of 100,000 (3). HDPE pipes, and their associated fittings and connections, offer a distinct advantage in that they can be used to create leak-free joints that prevent background leakage.

The transition fitting, for instance, is a permanent factory-made joint that connects HDPE pipe to any other pipe material. The joint is secured with an O-ring sealed, circumferential compressive fit of the HDPE pipe around or into the other pipe material. The transition fitting allows for the HDPE pipe to connect to steel pipe, ductile-iron pipe, PVC pipe, and more. Modern options that take advantage of fusion welding also exist.

The traditional approach calls for butt-fused welding, which creates a fusion joint that is leak-free and as strong as the pipe. During repairs or special service that requires a modification to the pipe that is not easily accessible, installers can use an electrofusion coupler to join the new pipe and fittings. Electrofusion is a computerized fusion process that eliminated most of the potential for human error while requiring a smaller access point for assembly.  Fusion offers a means of joining the HDPE piping components and creating one homogenous, leak free system.  

There are many more types of fittings and connections for HDPE pipes, which is partly as a result of its greater flexibility when compared with PVC and traditional piping materials. While the lack of stiffness means that HDPE pipes can be transported and installed easier, it also means that special fittings are sometimes required to connect the pipe to various components. To overcome this disadvantage, installers should consider sourcing their pipes and fittings of the same material.

HDPE pipes and fittings

One of the biggest advantages of sourcing your pipes and fittings from the same material is that you ensure optimal interoperability and minimize the risk of time-wasting modifications to accommodate for any differences between products. Some manufacturers go a step further by providing training and specialized equipment to work with their products. AGRU America, for instance, is an exclusive distributor of the HÜRNER line of electrofusion welders and offers training for installers looking to use the equipment for AGRU’s electrofusion couplers.

AGRU also manufacturers the largest HDPE diameter pipes and fittings in North America. These AGRU large-diameter, or XXL, HDPE pipes are sized between 24 IPS and 63 IPS OD and 1600 mm  to 3260 mm OD. Such supersized pipes are especially useful in creating the primary intake system for desalination plants or constructing the outfall pipe of a wastewater treatment facility.