Rainwater outlets are essential components of a building’s drainage system. Their primary purpose is to collect and discharge rainwater from roofs, balconies, and other horizontal surfaces, ensuring that water does not accumulate and cause damage to the structure or create safety hazards.

Overflow systems act as a backup drainage solution. If the primary roof outlet becomes blocked or overwhelmed, the overflow outlet allows excess water to escape, preventing ponding and potential flood damage to the building structure.

They are typically installed in the lowest points of a surface to allow gravity to direct water toward the outlet, from where it can be guided to downpipes or drainage systems.

• SPS and Metabronze Rainwater Outlet are designed to integrate with membranes and roofing systems to ensure watertight connections. Drains are compatible with EPDM, TPO, and Butynol membrane surfaces, as well as cement and asphalt toppings.
• SPS heavy-duty grates are engineered for vehicular crossing and are load tested to Class D of AS3996-2006.
• ‘SuperFlow’ rainwater drains, equipped with 150mm and 225mm outlets and larger grate dimensions — unique in New Zealand — provide exceptional water flow capacity. These drains are designed for areas prone to prolonged rainfall or flash flooding, ensuring reliable performance in challenging conditions.

Key Uses:

• Flat and Low-Slope Roofs: Designed to prevent water ponding on flat roofs by directing it into the drainage system.
• Terraces and Podium Decks: Collect rainwater to prevent infiltration into the building structure.
• Balconies and Walkways: Manage smaller volumes of runoff and prevent surface water buildup.
• Carpark Decks: Manage surface water efficiently in areas subjected to vehicular traffic and heavy load-bearing conditions.  

Benefits of Rainwater Outlets

• Structural Protection: Prevents water buildup that can cause leaks, mould, or structural weakening.
• Safety Enhancement: Reduces slip hazards from pooled water on walkways and decks.
• Aesthetic Preservation: Prevents unsightly water stains and damage on building exteriors.
• Supports Sustainable Drainage: Can be connected to rainwater harvesting systems or sustainable drainage systems.
• Prevents Roof Damage: Eliminates excessive load from standing water, which can deform or damage roofing systems.
• Compliance with Building Codes: Ensures buildings meet drainage regulations and best practices.
• Environmental Objectives: Metal components such as bronze, cast iron, and stainless steel are recyclable, supporting sustainability objectives and contributing to the long-term value of building assets.

Rainwater outlets are crucial in efficiently managing surface water and protecting buildings from water damage. Their design, material selection, and proper installation are essential for ensuring the long-term health of a structure’s roofing and drainage system. When chosen and maintained correctly, they provide a robust, low-maintenance, and sustainable solution to rainwater management.

• An insufficient number of roof drains and overflow units or the provision of outlet pipe sizing that is too small to handle infrequent weather events such as ‘flash flooding’ can lead to pooling and damage to the membrane and building. 
• Incorrect installation of roof drains into membrane surfaces can lead to leakage issues at the connection points with the membrane. Proper integration is crucial for maintaining effective waterproofing.
• The accumulation of debris on the roof, particularly around drains, can impair the effectiveness of the roof drain system.   

Installation Requirements 

• The design, size, and materials of a roof drain must be compatible with the membrane system used, environmental conditions, and location accessibility. 
• The number of roof drains installed per square metre of roofing and the location of each drain are also critical considerations when calculating rainwater clearance.
• Overflow drains should be incorporated within the roof drain system as a backup in case of blockages to the primary drains or pipe system.   
• Use a clamp ring system to secure the membrane to the drain outlet.
• If the Upstand (overflow) is required, install it between the ring/body and the grate.
• Use bolts to secure all parts as per manufacturer instructions.  
• Ensure compliance with all Building and Plumbing Standards.   
• Refer to product datasheet.

Maintenance & Preventative Measures 

• Keep the roof membrane free of debris to prevent pooling and potential moisture ingress.
• Avoid contact with any harmful chemical substances, i.e. petroleum, solvents, and kitchen fats. 
• Limit foot traffic on the roofing surface and use protective boards if equipment needs to be used within close proximity to the drain outlets.   
• Clean the roof annually, or 6 monthly depending on the environment, using appropriate methods and only use manufacturer-recommended cleaning agents. 
• Inspect and clean drains and gutters every 3-6 months, after severe weather, and following seasonal changes. Check around grates for excess dirt, debris, and fallen tree material. Clear as necessary.  
• Check for cracks around roof drains and repair them as required.
• Install a gravel guard or leaf guard to prevent debris from entering the drain.
• Inspect the roof membrane for signs of wear and damage, and repair or replace sections as needed.
• Over time, the membranes around drains may degrade or separate. Regular inspections and repairs will prevent leaks. 
• Hire professional roofing services to provide comprehensive inspections, expert maintenance, and repairs as required. 

SPS Rainwater Outlets are designed and manufactured to meet the requirements of the New Zealand Building Code (NZBC), specifically Clauses E1 (Surface Water) and E2 (External Moisture), along with their Acceptable Solutions E1/AS1 and E2/AS1.

NZBC Clause E1: Surface Water:

• Purpose: E1 requires buildings to manage surface water effectively, ensuring that rainwater is collected and disposed of so that it does not enter buildings or cause property damage.
• Compliance: SPS rainwater outlets are engineered to provide efficient drainage from roofs and other surfaces, minimising the risk of water ingress, blockages, or overflow. Their design and capacity align with the performance requirements of E1, ensuring surface water is safely directed away from the building envelope.
• Acceptable Solution (E1/AS1): By following the construction details and installation practices outlined in E1/AS1, SPS rainwater outlets are deemed to comply with the code. This includes correct sizing, placement, and integration with waterproofing systems to ensure reliable surface water disposal.

NZBC Clause E2: External Moisture:

• Purpose: E2 focuses on preventing external moisture from penetrating the building envelope, which could otherwise cause damage or health issues.
• Compliance: SPS rainwater outlets are compatible with modern waterproofing membranes (such as torch-on and TPO systems). Their robust construction, made from materials like stainless steel, cast iron, bronze, and aluminium, ensures long-term resistance to corrosion and moisture ingress.
• Acceptable Solution (E2/AS1): SPS outlets can be specified and installed under E2/AS1, which provides prescriptive methods for integrating drainage components with waterproofing systems at critical roof and deck junctions. This ensures that the outlets contribute to a continuous, watertight barrier as required by the code.

Additional Qualities Supporting Compliance:

• Watermark Certification: SPS rainwater outlets are Watermark Certified, confirming they meet relevant New Zealand and Australian standards for plumbing and drainage products.
• Independently Tested: Products are independently tested for performance, including water flow capacity and durability, supporting their suitability for code-compliant installations.
• Track Record: SPS products have a proven history of use in commercial and residential projects, demonstrating enduring performance and acceptance by building consent authorities.

Note: Compliance is contingent upon correct selection of the drain outlet size, the number of outlet drains provided for use, and the correct installation process.

SPS has a proven track record of supplying Rainwater Outlets to both commercial and residential markets for over 47 years, establishing itself as a trusted leader in drainage solutions. 

While SPS continually innovates and enhances its product lines, the core range of Rainwater Outlet products has been a mainstay in the market for more than three decades, reflecting their reliability, enduring performance, and strong market acceptance.

Metabronze and SPS Rainwater Outlets have been installed on the following projects:

• Auckland Airport Western Terminal Development
• Te Uru Apartments, Hobsonville
• Bowen House, Wellington
• Wellington International Airport
• Aotea Centre, Auckland
• Westfield Newmarket — 309 Broadway      

Waterflow Testing:

• SPS Rainwater Outlets and Metabronze Clamtite Drains have been independently Water Flow Rate Tested using recognised AHSCA Testing procedures. 

Load Rating: 

• SPS 100mm & 150mm ‘Truflo’ Rainwater Outlets, with Class D Heavy Duty Flat Grates are Load Tested to Class D of AS3996-2006. 
• SPS 150mm & 225mm ‘Superflo’ Rainwater Outlets, with Class D Heavy Duty Flat Grates are Load Tested to Class D of AS3996-2006. 

Watermark Certification

SPS Products have achieved the Watermark Certificate of Conformity:

• Certification Specification: WMTS 040:2022 Waste pipe connection outlets and gratings, separate or integral
• Product Type:  Waste Fittings 
• Product Use: Sanitary Drainage
• Brand: SPS  
• Issue Date: 1st April 2025
• Initial Issue Date: 28th August 2009
• Expiry Date: 27th June 2029
• Granted by: Pro-Switch Pty Ltd  
• Certificate No.: 20052 

Sustainability

With the selection of materials, primarily Bronze, Stainless Steel, and Cast Iron, Metabronze promotes environmental benefits and sustainability. Stainless Steel, Bronze, and Cast Iron will last for decades or longer, and can be recycled or repurposed at the end of their functional or economic life.

Warranty

• Specialty Plumbing Supplies Pty Ltd (SPS) warrants its products against defective components and faulty workmanship for a period of five (5) years. 
• Any defect in materials or workmanship occurring within five (5) years from the date of purchase subject to conditions will be rectified free of charge.