The continuous slot screens are constructed from triangular wire or plastic wrapped around a series of vertical rods. When properly sized, these screens are very efficient. Slotted pipe screens are constructed by making machine cut slots into either steel or plastic casing at prescribed distances. This type of screen has less open area than a continuous slot screen. They are moderately efficient.
Perforated pipe is a length of casing that has holes or slots drilled or cut into the pipe.
This type of screen is generally not very efficient and is not recommended for sand and gravel aquifers although it may be useful in semi-consolidated aquifers. Open hole completions are never recommended in unconsolidated aquifers. The proper screen slot size is determined by examining the well cuttings while drilling through the water bearing zone. Select a size that holds back the sand, yet allows water to freely enter the well. Choosing a slot size too small will hold back the sand but will also restrict the movement of water into the well lessening efficiency and increasing the stress on the pump.