Rain Water Tank 'First Flush' Filter Systems:

When it first starts to rain, water slowly builds up in the roof gutter system before it exits through the down pipe. The first flush of water from the roof can contain amounts of bacteria from decomposed insects, lizards, bird and animal droppings and concentrated tannic acid. It may also contain sediments, water borne heavy metals and chemical residues, all of which are undesirable elements to have in a water storage system.

Instead of flowing to the water tank, these pollutants are diverted with the initial flow of water into the chamber of the first flush system. As the water level in the diverter chamber rises, 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 through the T piece to the tank. 

The first flush system should be installed at each down pipe that supplies water to the tank.

They are simple and effective first flush devices and are installed to the down pipe. After the rain, just drain the system through the valve ready for the next rain. The bottom of the unit can be screwed off to fully clean the unit occasionally.

If you have overhanging trees and leaves in your gutters, first flush systems work best when a leaf catcher box is installed at the start of the down pipe. Fitted at the down pipe either directly on the underside of the roof gutter or to a wall, the device deflects leaves and debris away from the flow of rainwater.

Brackets for mounting the first flush device to the wall can be bought from your local hardware store, standard 110 mm round pipe brackets.   


·         8 Litre - 950 mm long, standard 110 mm diameter pipe: holds approximately 8 litres of water: R450 each.


·         8 Litre -   580 mm long, 160 mm diameter pipe: holds approximately 8 litres water: R490 each.


·        4 litre - 500 mm long and 110mm diameter pipe: holds approximately 4 litres water: R350 each. 


 80 mm round T pieces sold separately at R45 each. Adapters also available if you have asbestos or rectangular/square gutter down pipes.

Below are pictures of the 8 litre and 4 litre units, showing the drain valve, screw off end cap and ball. 

 Examples of installations: