32 HEALTH AND SANITATION
A rain garden is a shallow, landscaped depression designed to capture and absorb rainwater from roofs, driveways, or streets, allowing it to naturally infiltrate into the ground. Planted with grasses and flowering perennials, rain gardens offer a cost-effective and visually appealing solution for reducing runoff. In addition to managing stormwater, they help filter out pollutants and create habitats for butterflies, songbirds and other wildlife.
“ Catching and infiltrating the stormwater in smaller quantities helps to reduce peak flow rates and keeps the land from being overwhelmed. Soils can typically handle / process small quantities of pollutants, where the typical design is just to flush all the stormwater to a big basin, intensifying flow rates and pollutants,” she said.
The National Institute of Building Sciences, an independent, non-profit, nongovernmental organisation that supports advances in building science and technology, offers the Whole Building Design Guide( WBDG), which provides guidance on integrating various building systems and technologies to achieve high-performance, sustainable and resilient buildings.
The WBDG includes a section on LID, examples of which include:
• Engineered systems that filter stormwater from parking lots and impervious surfaces, such as bioretention cells, filter strips, and tree box filters.
• Engineered systems that retain( or store) storm water and slowly infiltrate water, such as sub-surface collection facilities under parking lots, bioretention cells and infiltration trenches.
• Modifications to infrastructure to decrease the amount of impervious surfaces such as curbless, gutterless and reduced-width streets.
• Low-tech vegetated areas that filter, direct and retain storm water such as rain gardens and bio-swales.
• Innovative materials that help break up( disconnect) impervious surfaces or are made of recycled material such as porous concrete, permeable pavers or site furnishings made of recycled waste.
• Water collection systems such as subsurface collection facilities, cisterns, or rain barrels.
• Native or site-appropriate vegetation.
If the goal is to retain and reuse the water at some point, cisterns or reservoirs are the better option.
Save it for later Underground cisterns and reservoirs can significantly enhance stormwater management, reducing runoff volume and maximising the use of space. Surface-level ponds and the like require valuable real estate, whereas subsurface cisterns, reservoirs or other storage means can be put under such areas as parking lots that were going to be developed anyway, leaving that additional area untouched and available for another purpose.
“ The real benefit of the underground cisterns is the capture of the water before it leaves the site to either slow it down or keep it from leaving the site at all through reuse practices,” Figola said.
Proper pipe sizing in these systems is vital, he said, pointing out that while most storm sewers are designed for a 10-year rainfall event on a private site, storms of significantly higher intensities than what they were designed for are becoming increasingly more common, leading to overland flooding and road overtopping.“ You need to make sure you’ ve properly sized for the volume of water that you’ re anticipating so that it gets where it needs to go and doesn’ t end up running off and flooding elsewhere,” he said.
Additionally, Figola said, large surface ponds can lose appreciable amounts of water through evaporation, which is particularly important in areas where water is scarce and every litre counts, and that is not as big of an issue when the water is stored underground.
Backflow prevention Sean Cleary, IAPMO vice-president of Industry Programs and Backflow Prevention Institute( BPI) Operations, said sizing of piping and water storage is a challenging task with many variables to consider. It must be based on numerous factors including normal rainfall, extreme weather conditions, drought, the intended usage of the system, peak demands on the system and possible other emergency water sources to make up for a lack of rain, snow or other normal resources used to supply the system.
In many cases, when system demand exceeds the available resources, potable water from the public water supply is used to make up for the necessary supply. Any connection between these systems either directly or indirectly is a crossconnection that requires backflow protection.
“ Because of the unknown quality of the storm or rainwater system, this connection must be considered a high-hazard situation that requires, in most cases, an airgap to separate the potable and non-potable water systems. If a direct connection is allowed, the protection would need to be provided by the installation of a reduced pressure principle assembly,” he said.
Need for trained professionals Trained design professionals – such as civil and mechanical engineers, landscape architects, architects and plumbers – are essential for effective and comprehensive stormwater management and flood mitigation plans. Without proper expertise, both soft and hardscape systems may be incorrectly sized, leading to dangerous consequences. Professionals must understand the calculations behind storm drainage design, ensuring systems can handle extreme rainfall events. Proper training helps reduce the risk of pipe bursts, roof collapses and overwhelmed landscapes by ensuring stormwater systems are correctly installed and maintained.
“ If they don ' t know the math behind it, they may put in the wrong size system without even knowing it because they ' re basing the decision making on faulty data. Having that additional training, having that additional expertise is definitely helpful in minimising that risk of a potential roof collapse or pipe bursting,” Lohr said.
Policy-driven resilience Policymakers play a crucial role in supporting plumbers and builders by developing and enforcing effective codes and standards for stormwater management and flood mitigation. By implementing regulations based on sound engineering principles, they help ensure that plumbing professionals have clear guidelines for designing and installing resilient systems. Additionally, policymakers can provide funding for training programmes, promote the adoption of advanced technologies, and encourage the use of sustainable infrastructure solutions. Their support is essential for creating safer communities by reducing the risks of system failures, property damage and public safety hazards during extreme weather events.
IAPMO senior director of Government Relations Jim Scarborough emphasised the importance of stronger infrastructure and federal assistance in rebuilding efforts.
“ If you want buildings and infrastructure to survive what they call once-in-acentury storms that seem to be happening every year now, then you ' ve got to build them stronger. It ' s hard to prepare for something when you’ re moving more than 40 feet of earth to take out underground pipes. That ' s just something you hardly ever experience; that ' s catastrophic. And I think in those cases, you ' re going to have to have federal dollars. The states are not going to be able to put up the kind of funding to recover from that by themselves,” he said.
“ As people become aware, as they see these weather events happening with such frequency, that may say more to legislators than anything.”
As climate change increases the frequency and intensity of storms, prioritising smarter stormwater management and flood mitigation strategies is essential. Properly designed and maintained systems – incorporating best practices such as adequate pipe sizing, green infrastructure and water reuse – enhance resilience and reduce long-term costs. Collaboration among plumbing professionals, engineers, policymakers and builders ensures that these systems remain effective and sustainable. Investing in innovative solutions and skilled professionals and labourers will help protect infrastructure, minimise property damage and strengthen communities against future challenges. PA
www. plumbingafrica. co. za @ plumbingonline @ plumbingonline @ PlumbingAfricaOnline May 2026 Volume 32 I Number 03