Sand Spears are a type of bore used in shallow (less than 6m depth) unconfined aquifers.
Shallow installations are usually used for delivering low quantities of water for watering a garden for example. Sand Spears come in both stainless steel V-wire or PVC. The design of the Stainless steel V- wire has some definite advantages over the PVC type for example:
- V-wires have a non-clogging surface
- They can cover a large open area
- Have a low pressure drop
- Are Hydraulic efficient
- They have high flow rates
- V-wire has mechanical strength
- It’s easy to clean
- It has a close slot tolerance
- Has a lower entrance velocity
- And they are used for better well development
For low-yield requirements a PVC sand spear may do the trick. It’s less expensive, non-corrosive, light weight and can easily be manufactured to suit your specific requirements.
For more information on the right Sand Spear for you, contact us
More on the Types of Sand Spears
Stainless Steel Wedge Wire Screen
Stainless steel wedge wire screens are the most common installation for DIY sand spears due to their robust construction and ability to withstand the “wash in” installation method. These spears can be constructed to just about any size aperture and flow based on your local ground conditions. Our stock stainless steel spears are made of 304 SS and come with threaded BSP fittings on both ends. These come with a 0.15mm aperture with a 5.7% to 9.7% open area providing 0.2 l/sec for a 600mm screen length. These screens have a 52mm ID x 60mm OD 70mm over fittings.
PVC Wedge Wire
The PVC wedge wire screens offer similar flow rates to the stainless-steel screens above with the budget in mind. While this material offers similar flow rates to the SS screens, we do not suggest installing these using the “wash in” method. While these screens are
not light weight in their construction, they simply don’t have the strength characteristics of steel. We suggest these are suited to a drop in method where the bore has been predrilled or excavated and gently manipulated into the sand with a wash-in valve.
These screens can be built to suit any ground conditions. Our stock screens are constructed with 0.25mm aperture with 7.7% open area providing 0.2L/s flow rate per 600mm screen length.
They come in 50mm, 100mm, 125mm and 150mm Nb
PVC Slotted Screen
These screens come in all sizes of pressure PVC sizes from 25mm to 375mm. Virtually any slot size and % open can be achieved to accommodate your specific ground conditions. Typical slot sizing for 50mm pn18 PVC is 0.4mm aperture with 10mm spacing providing a 2.4% open area and 0.3L/s flow rate (per 3m of screen).
This type of screen is more typically installed with a graded sand (8/16) filter pack that surrounds the screen and when installed in minimum 3m lengths. However, if you are just trying to achieve a modest amount of water then these can be used similarly to the sand spears above at a fraction of the costs. These screens are also more robust than the wedge wire PVC constructed screens and can be installed and removed several times before they become compromised. Caution should be used, and care taken during wash in installation as they are still PVC and do not have the impact strength characteristics of steel.