Downspout First Flush Water Diverters improve water quality and reduce tank/cistern maintenance by preventing the first flush of water, which may contain roof contaminants, from entering the tank/cistern. They help ensure cleaner water is available for use, which protects rainwater pumps and internal household appliances such as clothes washing machines, toilets, hot water systems, etc.
Downspout First Flush Diverters, such as the 3" kits, are installed at each downspout that supplies water to the tank/cistern. They utilize a dependable ball and seat system - a simple automatic system that does not rely on mechanical parts or manual intervention. As the water level rises in the diverter chamber, the ball floats, and once the chamber is full, the ball rests on a seat inside the diverter chamber preventing any further water entering the diverter. The subsequent flow of water is then automatically directed along the pipe system to the tank/cistern. This kit does not include the 3" pipe.
Features and Benefits
- Prevents sediment, bird droppings, spiders, insects, mosquito eggs and debris from entering the rainwater tank/cistern.
- Improves water quality, protects pumps and internal appliances.
- Ideal to use in conjunction with a rain head.
- Easy installation, just add pipe and glue.
- No mechanical parts.
- Low maintenance requirements
How much water to divert
It is important to prevent heavy sediments and other roof pollutants from entering the rainwater tank/cistern. The amount of water diverted should be a minimum of 12.5 gallons per 1000 square feet of roof area (or 0.0125 gallons per square foot). In calculating the amount of water to divert, consideration can be given to (1) the surface area of the roof, and (2) the amount of pollutants on the roof and gutters.
The following factors can be used as a guide in determining the volume of water to be diverted.
As a rule of thumb, the more water that is diverted the better the quality of water in the tank/cistern.
1. Determine the length of Diverter Chamber #4. Consider as a guide
– 3 foot section of 3" Schedule 40 PVC pipe holds approx. 1.5 gallons
Fit the longest length of pipe possible, making sure the Screw Cap
#10 is at least 6" from the ground to allow for removal and
2. Place the ball Seat #9 into the Tee Junction #6 ensuring the narrow
end of the ball seat points down into the Diverter Chamber #4. Apply
glue to the Diverter Chamber #4 and fit up against the Ball Seat #9
and hold until the glue sets. (Optional: Use a 45º bend adaptor to
allow easier removal of the Screw Cap #10). Glue the Socket #14 to
the bottom end of the Diverter Chamber #4.
3. Fix the assembled chamber directly to the wall in the desired position
using the Wall Brackets.
4. Connect a Male & Female (M&F) Elbow #8b (if required) to the
Chamber Outlet #8 and connect the downspout #3. Fit an elbow to
the InFeed pipe #2 (if required) and connect to the bottom of the
selected rain head.
5. Select the appropriate Flow Control Valve #11 and insert into the
Hose Connector #16, making sure the valve is inserted with the side
marked "TOP" still showing. Start by using the Control Washer with
the smallest gauge hole (lowest number). Try a larger gauge Washer
if experiencing blockages. Place the Filter Screen #13 into position
from the outside of the Screw Cap #10 and then attach the Hose
An extra filter screen that helps stop the Control Valve blocking is
available from your local store. Ask for the "Optional Stainless Steel
Primary Screen" (Product Code: WDAC02). This filter is fitted in
addition to the Plastic Filter Screen #13. To install: After completing
step 5, insert the Keeper Ring #1a into the Screen Cap #10 and then
place the Optional Stainless Steel Primary Screen on top of the Keeper
Ring #1a. Proceed to step 6.
6. Place the Sealing Ball #5 into the Diverter Chamber #4 and attach the
assembled Screw Cap #10 to the Socket #14.