There are two stormwater management approaches: retention and detention. Retention aims to limit the outlet flow into existing sewers or channels, while allowing some stored runoff to recharge groundwater levels. Detention uses a watertight system to redirect flow to only the regulated discharge outlets. In the past, reinforced concrete pipe (RCP) was the primary piping solution. Today, RCP’s plastic counterpart high-density polyethylene (HDPE) has proven itself not only a long-term cost-effective alternative, but also a problem-solving tool to add to an engineer’s repertoire (1).
Read on to learn about the differences between RCP and HDPE pipe, HDPE advantages, and how to design your own HDPE stormwater management system.
HDPE pipe vs. RCP: A matter of longevity
Reinforced concrete pipes have served us well, but they have proven themselves costly to sustain. It is more expensive, and time consuming, to go back and rehabilitate RCP than it is to repair HDPE pipes. There are many environmental factors that can increase repair intervals for RCP. In 2004, a town near the coast of Texas found itself in need of replacing its existing RCP stormwater system (2). Poor backfill, from sandy soil and a high groundwater table, caused bell-and-spigot joint failure. The environmental challenge compelled innovation in the form of a new piping product choice.
HDPE joints are watertight as the pipe and joints are fusion welded together, needing no extra couplers, grout, or other sealants to install. This type of joint meets or exceeds ASTM 3212 lab test and ASTM 1417 watertight field test and meets Environmental Protection Agency guidelines. Cost efficiency also comes in the form of uninterrupted water flow. HDPE pipes are resistant to chemical, biological, and abrasive damage, promoting a smooth surface, hence better and perhaps more importantly, sustained Manning’s roughness coefficients, throughout the lifetime of the pipe.
HDPE pipe advantages
Beyond longevity, HDPE delivers many worthy benefits such as reduced construction times, environmental sustainability, energy efficiency, long service life, leak free protection, custom designs and layout, and more. HDPE also outperforms other piping alternatives in its stability during seismic activity, presenting resistance to stress cracking and deformation. Beyond performance, HDPE pipe is easier to handle during construction.
Prefabricated joints and fittings, for instance, help reduce onsite construction time. You can even find suppliers who manufacture pipes and all associated fittings to ensure greatest compatibility. HDPE pipe is also often the environmentally sustainable choice. For instance, HDPE pipe supports trenchless installation methods such as horizontal directional drilling (HDD) if pipes must be installed near an ecologically sensitive area. HDPE pipe is also more energy efficient to manufacture and transport when compared with PVC and iron pipes (3). Finally, its strength, low weight, and flexibility supports unique designs and sizes.
- “Stormwater management.” PPI https://plasticpipe.org/drainage/cppa-stormwater.html.
- “When plastic is more than concrete: Texas town tries HDPE pipe in storm water applications.” Waterworld (2014). https://www.waterworld.com/articles/2004/11/when-plastic-is-more-than-concrete-texas-town-tries-hdpe-pipe-in-stormwater-applications.html.
- Du et al., “Life cycle analysis for water and wastewater pipe materials.” J. Environ. Eng. 139:703-711. (2013). http://oceanpipe.com/sites/default/files/pdfs/resources/Pipe%20-%20Lifecycle%20Analysis%20for%20Water%20Wastewater%20Pipe.pdf.