* During the jetting process, water emerges from the end of the jetting pipe and flows upwards to ground level. If the flow of water stops (e.g. water runs out, or to change a pipe), in most circumstances the sand around the jetting pipe/screen will collapse, after which it is impossible to re-start the flow of water to the surface. However, in some cases the hole will remain open – only in these cases can you add another pipe and continue jetting, but otherwise the depth you can install the screen is dependent on the length of jetting that can be done in one go without stopping the pump.
* Digging a large pit to the water table is advantageous since:
# In collapsing sands, you can jet to the base of the pit, after which you can glue extra pipes onto the screen to reach ground levelso level, so that a deeper well is achieved.
# The chance of losing the water column is minimized due to less pressure head that the water must overcome in order to flow to the surface. With higher pressure heads (i.e. more distance from water level in ground to ground level), the water is more likely to choose the path of least resistance, which at some point will be to go into the aquifer rather than come to the surface. In such a case where you lose the water column in collapsing sands, the well will be finished at that depth.
* A screen can have a ball valve at the end – in this case, the jetting pipe and screen are made from the same piece. Alternatively the screen can be separate from the jetting pipe, where the jetting pipe creates the hole and then is removed once the screen is installed to required depth. If a screen with valve is chosen, care should be taken if installing handpumps as the ball valve has a tendency to open over time letting in sand.
