In Ground Diverters

First Flush Water Diverters


Description Code
In-Ground First Flush
Water Diverter
12″ WDIG99
(12″ DIAM. PIPE)
Volume in US
contained (approx.)
2 77 Add the volume of water held in the pipe section downstream of the Diverter, between the Chamber and the Flow Control Valve/Outlet. For every 3 feet of 4″ PVC pipe add 2 gallons.
4 112
6 147
8 182
10 218
12 253
14 289
16 324
18 360
20 395

Buried and out of sight, In-Ground Water Diverters are perfect for sloping allotments. On a site that provides the opportunity for the end cap of the  diverter to be positioned above ground (to drain out and be accessible for maintenance), an In-Ground Diverter allows a ‘wet’ system to be converted into a ‘dry’ system.

Most systems are ‘wet’ due to the size of buildings, and the placement of tanks away from the buildings mean that there are long runs of pipe underground leading to a riser at the tank. On a sloping site this diverter ensures the diverted water and the water that would normally remain in the pipes empties out. The result – a ‘dry’ system that improves water quality.

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.
  • Perfect for sloping allotments.
  • No mechanical parts.
  • Inlet fits 3″ Schedule 40 pipe or 4″ Schedule 40 female coupling.
  • Easy installation – just add pipe and glue.
  • Low maintenance.
  • Converts a ‘wet’ system in to a ‘dry’ system.



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 carrying water from the roof can be directed into an In-Ground Water Diverter.



Installation Instructions

Determine the length of 12″ pipe required using the table.

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 in the attached drawing making sure to insert ball #7 before attaching cap #11. Select one of the four control valves #12 and fit into hose connector #13. Save the remaining valves for possible later use.