Protect the quality of your collected rainwater with first flush systems that divert initial runoff and keep debris out of your storage. The following five products are designed to minimize contaminants, reduce clogs, and simplify maintenance for residential rainwater harvesting setups. Each option offers distinct features—from auto-drain functionality to catch-all tees—so you can choose the system that best fits your downspout size and volume needs.
| Product | Brand | Key Benefit |
|---|---|---|
| Rain Harvesting First Flush with Catch-All Tee | Rain Harvesting | Auto-drains; Catch-All Tee prevents premature flow |
| Rain Harvesting First Flush Downspout | Rain Harvesting | Easy installation; auto-draining chamber |
| Rain Harvesting WDDP111 Downpipe First Flush | Rain Harvesting | Compact 4″ round fit; lightweight |
| Rain Harvesting Carrot 3″ | Rain Harvesting | Chamberless design; automatic reversion after flush |
| Best Downspout Diverter | Generic | Universal downspout fit; self-flushing to reduce clogs |
Rain Harvesting First Flush With Catch-All Tee
The First Flush with Catch-All Tee diverts the initial roof runoff through a dedicated chamber, ensuring only high-quality water enters the storage tank. The Catch-All Tee design prevents premature flow across the tee, stopping contaminated water from advancing. An auto-draining feature slowly releases water from the chamber during rainfall events, keeping the device ready for the next rainfall.
Rain Harvesting First Flush Downspout
This first flush kit is designed to divert initial runoff to maintain water quality. It features an auto-draining chamber with a slow-release valve, preparing the system for the next rainfall. The kit includes everything needed for installation—simply add 3″ pipe to complete the chamber.
Rain Harvesting WDDP111 Downpipe First Flush
Compact in size, the WDDP111 Downpipe First Flush Diverter fits standard 4-inch round downpipes and maintains a lightweight profile. Its dimensions (11.6 x 9 x 5.7 in.) and modest weight (3.3 pounds) make it a user-friendly option for smaller setups while still providing effective initial runoff diversion.
Rain Harvesting Carrot 3″ First Flush
The Carrot 3″ model features a compact, chamberless design that uses a Catch-All Tee and adjustable flow to divert approximately 5 gallons from the initial runoff. It automatically reverts after the flush, making it suitable for medium catchment areas with moderate pollution and a simpler installation approach compared with chambered systems.
Best Downspout Diverter
Designed to fit a wide range of downspouts, this diverter kit emphasizes a patented, high-efficiency flow path with self-flushing capabilities to minimize clogs. It supports various configurations and works with rain barrels, water tanks, and cisterns when paired with standard downspouts. It includes adapters and reducers for DIY installation and aims to reduce debris entry into the storage system.
Anivia Rainwater Collection System
The Anivia Downspout Diverter fits 2×3 or 3×4 inch downspouts and includes a removable filter window and filter net for debris removal, promoting clearer water collection. It provides adjustable flow via a switch valve (OFF/Medium/High) to tailor capture to your garden needs and conserve water when appropriate. A 5-foot hose adds flexibility for directing water to irrigation zones.
Buying Guide
- Downspout compatibility: Verify pipe size (3″, 4″, or universal downspout fittings) to ensure a secure fit with your existing system.
- Flow control and flush design: Consider whether you prefer a chambered system with auto-drain or a compact, chamberless design and adjustable flow to match rainfall patterns in your area.
- Maintenance considerations: Look for features like Catch-All Tees, removable filters, and easy-clean access to minimize ongoing upkeep.
- Installation effort: Some kits require only addition of pipe segments, while others include more components. Assess your DIY comfort level and required tools.
- System footprint: Evaluate the space around your downspout and rain barrel to ensure the first flush unit fits without obstructing access or drainage pathways.
- Material durability: Preference for weather-resistant plastics and corrosion-resistant components can extend the life of the diverter, especially in harsh climates.
- Water quality goals: If you need higher purity for irrigation or household use, prioritize units with robust filtration or catchment controls like Catch-All Tees and easy cleaning features.
- Cost vs. benefit: Weigh the initial installation effort and parts against potential savings from reduced debris and improved water quality over time.
All options listed are designed to improve rainwater quality entering your storage system and help protect downstream filtration or irrigation equipment. Consider your roof type, typical rainfall, and the size of your rain barrel when selecting a first-flush solution.