The Sand Filter system is a variation of the Watersave system, as designed by GRS. Greywater is first directed to a 1200 x 1200 mm sedimentation tank and then passes through a stone and sand filter before it is pumped through a subsurface dripper system. The pump chamber is on top of a sand-stone filter.
Sand Filter System
In the GRS Sand Filter Irrigation System, the greywater enters the bottom of the tank, is spread through the floor via 100 mm drain coil pipe and then proceeds to move upwards through the stone and sand layers.
The sand is coarse river sand which has been shown to contain 83% of particles 0.5 to 2 mm, and smaller percentages of slightly larger grains and silt. Its red colour suggests an iron content, which is expected to remove some phosphate from the wastewater.
The effective volume of stone and sand is about 225 L each. This is adequate to filter the greywater to enable effective suspended solids removal for irrigation via drippers.
The sand and stone filter (450 L) is only a secondary filtration system - to ensure that blockage of the dripper system does not occur. However, a standard in-line irrigation filter is also placed before the dripper system to remove any sand which may be inadvertently pumped from the tank.
The remainder of the tank is the pump chamber. It is estimated that the capacity will be about 750L, of which 600 L will be pumped at any one time. A submersible pump with float switch, such as those produced by Davey or Grunfos, will be used.
The recycled greywater will be pumped to areas of the garden through standard irrigation pipe to a network of subsurface drippers as part of the Netafim pipe Uniram (purple dripperline, also known as Unibioline). Drippers at set at 300 mm and 2.3 L/h.
Tiran 17 pipe has a dripper rate of between 8 and 10 L/h. A 100 mm layer of mulch is placed on top of the irrigation pipe.
Each line (lateral) will have a flushing valve on the end of the line to flush residual solids. At least one vacuum breaker should also be installed at the highest point in the irrigation layout.
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Greywater Reuse Systems (GRS) became Water Installations Pty Ltd in 2007.
GRS still operates the part of the business that deals with the manufacture, supply and installation of greywater systems.
GRS have many systems approved for use in WA, some of which can be found at the retail outlet at Unit 1, 18 Wandeara Crescent, Mundaring.
Ross Mars is the Managing Director of Water Installations Pty Ltd.
He is a well-known Western Australian educator, writer and course and workshop presenter.
He completed a PhD in Environmental Science at Murdoch University in 2001.
His research centred on the use of native wetland plants to strip nutrients from domestic greywater.
Ross also has qualifications in Permaculture, and offers general Permaculture courses (Permaculture Design Course) as well as Accredited Permaculture Training.
Details of these can be found on his Candlelight Farm website.