Most water bores in Perth that are drilled by the rotary mud method have a length of slotted PVC or stainless steel screen at the bottom to allow the water in to the borehole.
Finely slotted Class 9 PVC bore casing is usually used for the bottom 6 metres of the water bore.
Much as we want plenty of water to flow in we want to keep fine sands and silt out as much as possible. This is the job of the gravel packing envelope.
See where gravel packing comes from in this video.
Around the screen, the drilled bore hole is a wider diameter than the bore casing itself. This area is called the annulus. The annulus is packed with carefully graded driller’s gravel to act as a primary filter.
Genuine drillers gravel is graded and washed coarse river sand.
A lot of care is taken to make sure this drillers gravel is perfectly suited for the task. Most drillers gravel used in Perth bores comes from near Carnarvon.
Watch as bags of graded driller’s gravel are added to this submersible garden bore just drilled in Myaree.
Bags of graded drillers gravel ready to pack around the slotted bore casing as a primary filter.
Gravel packing for a school oval bore. Lots required!