Post/Wall Water Diverters

First Flush Water Diverters


Description Code
Post/Wall Mounted First Flush Water Diverter
12″ WDPW99″
to Divert
Pipe Diverter
Total Height
6 12 26
9 18 32
12 24 38
15 30 44
18 36 50
21 42 56
23 48 62
26 54 68
29 60 74
32 66 80
35 72 86
38 78 92

The First Flush Post/Wall Stand Water Diverter is a versatile unit that can be mounted on a wall or post, to hold larger volumes of water. It can be adapted to suit a wide range of applications and will manage single or multiple pipes coming from the roof to divert between 6 and 38 gallons.

The kit is easy to freight, and the diverter volume can be made on site to match exact requirements – just add the appropriate length of 12″ pipe. The kit includes a saddle and a galvanised steel wall-mounting bracket.

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 12″ pipe length and glue.
  • No mechanical parts.
  • Inlet fits 3″ Schedule 40 PVC pipe or 4″ Schedule 40 female coupling.
  • Low maintenance

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.

Multi pipe feed systems

These water diverters can handle more than one pipe

Single or multiple pipes coming from the roof can be connected into a “T” and coupled together so that the first flush from the roof enters the diverter chamber. The pipes are connected from the “T” into the tank/cistern.


Installation Instructions

Determine the length of pipe required using the table above.

Inlet End: The ball seat #6 is inserted into the top of the end cap as shown.
– For 3″ Schedule 40 PVC pipe infeed – insert the ball seat #6 and attach
the infeed pipe hard down on top of ball seat #6.
– For 4″ Schedule 40 PVC pipe infeed – insert the ball seat #6 and glue
the 3″ keeper ring (1.1″ long) hard down on top of the ball seat #6 to
keep it firmly in place.

Outlet End: The outlet requires only 3″ pipe. Assemble as shown making sure to insert ball #7 before attaching cap #12. Select one of the four control valves #13 and fit into hose connector #14. Save the remaining valves for possible later use.