According to the Environmental Protection Agency, at least 12% of U.S. household water usage is wasted as a result of leaks in water piping systems. According to estimates by the America Society of Civils Engineers (ASCE), the loss represents over 6 billion gallons of treated water. The strain on the infrastructure necessitates enormous effort to repair and replace, estimated to exceed several hundreds of billion dollars. These pipe issues will only become harder to correct, because many systems have been pushed beyond the limits of their design. Municipal water systems have been strained for decades, especially in cities with population booms following the industrial revolution. Today, water companies and municipalities are on the lookout for viable piping alternatives that are durable, inexpensive to maintain, and safe for human use.
One candidate material is high-density polyethylene (HDPE), which has been used for decades as a highly reliable and durable piping material. During this time, the advantages of PE pipe for water supply applications has been extensively published. The real-world benefits of HDPE water pipe systems are not limited to the United States. On a global basis, piping system designers and engineers have embraced the potential for addressing major water-related infrastructure issues. Read on to explore several notable applications of PE pipe for water supply.
Rebuilding a water transportation network with polyethylene
Following World War II, the city of Palermo, Italy grew from 300,000 to over 700,000. Residual damage from the war along with the increased water demand from the growing population put a huge strain on the aging cast iron water network. In some parts of the network, water leakage rates exceeded 40%. In 1990, the city planners and an Italian water company designed a plan for a water network capable of delivering 430 liters per inhabitant per day for a projected population of a million citizens. The system was designed to last through to 2040. To meet these requirements, HDPE pipe was chosen thanks to its lightweight and flexibility, enabling fast installation and fewer fittings. Additionally, the ability to join HDPE pipe with heat fusion provided the highest potential that leak-proof joints within the system would be achieved.
A one-year follow-up on the installation demonstrated satisfactory results.
Installing a new HDPE pipe line along an uneven waterway
The small town of Grand Island, Louisiana had once been able to sufficiently supply its small population with clean drinking water through an 8-inch cast iron pipe. By the 1990s, however, over 7,500 people were dependent on that same system for clean water, which proved unsustainable.
A solution was proposed in the form of a 32 mile 16-inch HDPE piping system. The pipe was designed to be laid along the Barataria waterway to bring fresh water from a nearby site. Although the design had been proposed before, it only became feasible with the use of HDPE. Other piping materials raised concern about joint integrity and overall pipeline stability in the marsh-like conditions of Louisiana.
Ultimately, thanks to the ability to heat-fuse the joints between HDPE pipes—as well as the pipe’s inherent flexibility—the team was able to install the 32-mile of pipe in less than half the expected time. Fast installation with a minimal footprint is essential for water works built in and around environmentally sensitive areas. Such was the case for HDPE pipe used in the Barataria waterway.
HDPE supports many installation methods beyond the method used at Grand Island, including horizontal directional drilling (HDD). HDD has proven to be one of the least invasive and most cost-effective pipe installation techniques available, and HDPE works well with the approach.
Horizontal directional drilling with HDPE pipe
By the late 1990s, sandwiched between the ocean and very steep hills, the rapidly developing city of Carlsbad, California was soon expanding further to the east past the range of its existing infrastructure. The need to bring water to the new developments presented a unique challenge: to cost-effectively develop a pipeline uphill and below a large interstate highway while also taking into consideration the local environment.
HDD was determined to be the best approach. Not only was it a trenchless installation technique with minimal surface footprint, the direction of the drilling can be controlled to avoid obstacles such as the interstate. HDPE pipe complemented the installation technique as a result of the material’s high strength, flexibility, and ability to endure minor surface perturbations during installation without damaging the pipe’s integrity.
The project was completed by 2001 ahead of schedule and below the projected budget.
Qualities that make HDPE pipes ideal for water supply solutions
HDPE pipes possess a number of traits that make it an ideal candidate material for the transport of water.
From direct burial, to slip-lining of an existing pipeline to horizontal directions drilling, HDPE pipe’s joint strength and long-term ductility make it well suited for many installation techniques and the most demanding service conditions. There too, HDPE’s flexibility can often be leveraged to minimize the need for some fittings thereby improving the hydraulic efficiency of the system.
From an operational point of view, the integrity of the butt heat fusion method of joining assures the designer that the potential loss of water through system joints will be minimal. Additionally, the potential for infiltration of contaminant into the water system from the surrounding soil through gasketed or mechanical connections is eliminated.
HDPE pipes are hydraulically efficient, meaning that the internal surface is uniformly smooth. More significantly, the smoothness factor does not change over time unlike pipes made with other materials that are affected by corrosion, tuberculation, or biological build-up.
HDPE piping is tolerant to nearly all types of environmental influences such as salt water, corrosive soils and/or aggressive flow streams. As a result. HDPE is an ideal material for the transport of potable water. The installed pipe will not corrode or degrade over time and there is no need for cathodic protection of the HDPE itself.
Durability is perhaps the most attractive feature of a pipe made with PE. The durability contributes to the pipe’s ease-of-installation and high service life (50 to 100 years), which in turn makes it a cost-effective system to implement. From a life-cycle cost perspective, HDPE pipe is one of the most attractive piping materials to be considered for water pipe applications.
- Sandstrum, Steve. “Case Studies in High Density Polyethylene (HDPE) Water Distribution Systems.” Water Works Assoc. Ann. Conf. (2003).
- “2017 Infrastructure Report Card.” American Society of Civil Engineer, Reston, VA.
- “PPI Handbook of Polyethylene Pipe (2nd Edition).” Plastics Pipe Institute. Chapters 1 and 3. http://plasticpipe.org/publications/pe-handbook.html. Accessed November 29, 2017.
- Ambrose, M., et al., “Life Cycle Analysis of Water Networks.” Proceedings of Plastics Pipes XIV, Budapest, Hungary (2008).