Improve Rainwater Quality Before It Reaches Your Tank The First Flush Downpipe Diverter by Blue Mountain Co helps improve rainwater quality by diverting the first, most contaminated flow of water from your roof before it enters your tank. This initial runoff often contains dirt, leaves, bird droppings, dust, and other contaminants collected between rainfall events. As the diversion chamber fills, an internal sealing ball rises to block the inlet, automatically redirecting cleaner rainwater to your storage tank. A slow-release drain valve then empties the chamber over time, preparing the system for the next rainfall event. Part Number: WDDP01 | Size: 90mm Part Number: WDDP02 | Size: 100mm The system can be customised by adding pipe length to suit your roof size and local conditions. Specifications Brand Blue Mountain Co Model First Flush Downpipe Diverter - Original Material UPVC Colour White Available Models WDDP01 (90mm), WDDP02 (100mm) Application Diverting initial contaminated roof runoff from entering rainwater tank Compatibility Rainwater bladder tanks, above/below ground tanks What's in the Box: First Flush Diverter unit + all fittings needed for setup (pipe not included – add your own to create storage chamber) Sizing Guidelines – Pipe Length Selection ▼ Select the length of pipe for your first flush diverter based on your roof area and environmental conditions. 🌿 Less Pollution Low debris, leaves, bird droppings, and animal matter.Divert approximately 0.5 litres per square metre of roof. Diverter Size Pipe Length per Square Metre 90mm (WDDP01) ~80mm 100mm (WDDP02) ~65mm ⚠️ Higher Pollution More leaves, debris, bird droppings, and animal matter.Divert approximately 1–2 litres per square metre of roof. Diverter Size Pipe Length per Square Metre 90mm (WDDP01) ~160mm to 320mm 100mm (WDDP02) ~130mm to 260mm How It Works – First Flush Diverter ▼ 1 First flush enters – The initial contaminated roof water enters the diverter chamber via a T junction or high flow inlet. 2 Chamber fills – The chamber fills with dirty water while a floating ball rises with the water level. 3 Ball seals the inlet – Once the chamber is full, the ball seals the inlet, blocking further dirty water from entering. 4 Clean water flows to tank – Cleaner subsequent rainwater flows directly to your rainwater tank. 5 Auto-drain resets system – Slow release valve automatically drains the chamber over time, readying the system for the next rainfall event.
