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As climate change and growing populations put immense pressure on limited freshwater resources worldwide, sustainable water management practices like rainwater harvesting are becoming increasingly essential. Collecting and repurposing rainwater reduces strain on municipal water supplies, decreases utility bills, and provides greater water security and self-sufficiency.

Implementing a well-designed rainwater harvesting system offers numerous environmental and economic benefits. Capturing rainwater from rooftops and other impervious surfaces can provide a reliable supplemental source of water for non-potable uses like irrigation, laundry, cleaning, and flushing toilets. This conserved water helps preserve precious drinking water for human consumption and essential needs.

However, proper drainage and diversion solutions are crucial to reap the full advantages of rainwater harvesting. Without effective drainage, excess rainwater can lead to flooding, erosion, structural damage, and overflowing collection tanks. Carefully engineered outdoor drainage systems specifically for rainwater harvesting applications can help collect every drop of runoff and channel it to storage solutions or dispersal points.

We’ll look at design considerations, integration with storage tanks, maintenance best practices, and how to choose the right drainage solutions for your site’s unique needs. With proper drainage, your rainwater harvesting system can operate optimally year-round while promoting sustainability.

The Benefits of Harvesting Rainwater

Implementing rainwater harvesting provides numerous advantages, both environmentally and economically. It conserves municipal freshwater supplies and local groundwater reserves by providing an alternative source for non-essential uses, allowing more drinking water to remain for human consumption and critical needs. Significant financial savings come from lower water bills when rainwater is used for irrigation, laundry, cleaning and toilet flushing instead of tap water from the mains.


Rainwater harvesting also provides a supply independent of municipal infrastructure, making it immune to restrictions, droughts or service disruptions that can disrupt mains supply. This bolsters self-reliance. Harvesting rain promotes sustainability by utilising nature’s hydrologic cycle and a free, renewable resource rather than limited reservoirs. The collected rain can be used for many purposes beyond drinking, including irrigation, car washing, fire suppression and flushing toilets. With proper filtration, harvested rainwater may even become potable.

Harvesting your rainwater also helps mitigate drought, climate change and chronic water scarcity by providing a buffer against shortages and improving water security. It benefits the environment by reducing stormwater runoff, recharging groundwater aquifers, and decreasing central supply systems’ energy use and chemical treatment needs. 

Understanding Drainage for Rainwater Harvesting

Properly designed outdoor drainage systems are crucial for managing excess rainwater in harvesting setups. Without effective drainage, excess water can lead to a number of problems:

Specially engineered drainage solutions for rainwater harvesting divert, control, and transport runoff efficiently to the desired collection points or dispersal areas. Options like trench drains, catch basins, and French drains strategically help collect rainwater from key hardscapes like rooftops, patios, driveways, retaining walls, and paved surfaces.

Carefully designed drainage and storage systems work hand in hand to direct, capture, and reserve as much rainwater as possible for reuse. Drainage provides a critical first step in routing runoff to cisterns, tanks, ponds or other storage media for maximum utilisation and water savings. Integrating drainage and storage is key to an optimal rainwater harvesting system.

Outdoor Drain Options for Rainwater Harvesting

There are numerous types of outdoor drainage systems well-suited for rainwater harvesting applications:


Trench Drains

Linear channels installed at ground level capture and divert surface runoff through a grated cover. They prevent pooling and flooding in high runoff areas like driveways, patios, and pathways. Trench drains come in various sizes and materials, like plastic or concrete.

Catch Basins 

Also known as storm drain inlets, these receptacles have an opening covered by a grated lid that collects and channels rainwater runoff into underground drainage pipes. Catch basins are typically installed in topographic low points where water naturally flows and accumulates.

French Drains

 Consists of perforated pipes wrapped in a gravel backfill within a trench. The gravel trench provides subsurface drainage that disperses and redirects excess rainwater into the surrounding soil. They are useful for diverting runoff away from saturated areas or structures prone to flooding.

Roof Drain Filters 

Installed inline between roof drain gutter downspouts and collection tanks. The filter basket catches leaves, grit and debris that would otherwise wash directly into your storage tank and clog pipes or contaminate water. This is crucial for a low-maintenance system.

Rain Chains 

Typically used in place of traditional downspouts. These chains slow and aerate runoff from gutter downspouts while being an artistic focal point. Rain chains deposit water into rain barrels or cisterns.


Design Considerations for Drainage Systems

When designing drainage capacity, it is important to account for local rainfall patterns, including total annual precipitation and peak storm intensities. Drainage components should be sized to handle the maximum expected volumes and flow to prevent overflow. 

Using recommended grading and slopes leverages gravity drainage while preventing stagnant puddles in low spots. Carefully grading surfaces and components to facilitate gravity flow avoids the need for pumps.


Piping is also a key consideration. Choose pipe diameters sufficient to accommodate peak stormwater runoff rates from the collection area. Oversizing is better than undersizing to handle extreme events. Also, incorporate emergency overflows that safely redirect excess volumes away from structures if storage tanks become overwhelmed. Specifying durable, corrosion-resistant materials like stainless steel mesh or PVC minimises long-term maintenance needs.

Consulting qualified drainage specialists is highly recommended to optimise your system’s design. They can survey your unique site characteristics, identify problem areas, take precise measurements, and recommend solutions tailored to your goals, landscape and budget. 

Maintaining Your Drainage System


Like other components in a rainwater harvesting system, the outdoor drainage system requires regular maintenance and upkeep to sustain optimal performance. Periodically inspect key drainage points and pipes to check for signs of clogging or blockages from accumulated leaves, grit and other debris. Use a hose to remove debris and clear any minor clogs before they worsen.

When rain occurs, visually monitor your drains to ensure water flows adequately. Heavy flows after storms help dislodge accumulated sediment and organic matter. Annually clean drainage pipes and grit removal filters to prevent slow flows and flooding.

Check trench drains, catch basins, overflow points and other components for cracks, misalignments, sinkholes or other damage. Use caulk, patches and braces to repair issues and prevent soil leakage or pipe detachment. Inspect gravel backfill in French drains to ensure the media is not compacted or clogged.

Monitor your drainage capacity over time, especially if collection areas expand. Insufficient drainage is a clue it may be time to upgrade pipes, add new drains or increase storage volume. Routine maintenance lets you address issues proactively before major overflows or failures occur. Investing in regular upkeep of your drainage infrastructure pays off through an efficiently functioning system.

Integrating Drainage With Rainwater Storage

For maximum efficiency in a rainwater harvesting system, it is essential to properly integrate the drainage components with the storage tanks or barrels that will hold the captured water. Carefully plan your storage capacity to accommodate average rainfall volumes and peak storm runoff amounts. The last thing you want is storage tanks to overflow every heavy storm.

Install emergency overflow mechanisms like secondary drains to safely redirect excess water away from structures if your storage volume is exceeded. Overflow pipes should drain away from the building’s foundation.

With thoughtful design, you can channel collected drainage from multiple downspouts, drains and other collection points across your site into a centralised storage hub, taking advantage of gravity flow. Using the landscape’s contours to your advantage avoids the need for pumps. Consider installing an inline purification or filtering system to remove debris, sediments and contaminants before the storage tank. This prevents build-up and keeps water clean.

Getting the drainage and storage solutions working in harmony is key to optimising your rainwater harvesting system. Contact our team of experts at Gold Coast Plumbing Experts today. We can survey your property, understand your goals, and recommend integrated drainage and storage designs suited specifically to your site. Start harvesting free rainwater today!