The FLUTe liner is often installed in the vadose zone to seal the hole against flow and to stabilize the hole wall. Several kinds of installation procedures are used. In most cases, the liner is everted into the hole (see everting liner mechanism). For other situations, the liner is lowered into the hole, as when the hole is supported by a temporary casing, and then filled with sand as the casing is withdrawn. In all cases, the flexible liner provides a seal against the hole wall.
The sampling geometry is shown in the drawing. 
The spacer material on the outside of the liner serves to define the interval of the hole from which the sample will be drawn. As the pressure is reduced in the sampling tube at the surface, the pressure is reduced in the spacer material interstices. This low-pressure draws pore gas into the spacer and hence into the tube to the surface via the port through the liner. If the spacer is relatively short, the pressure field near the spacer is essentially a spherical 1-D flow field centered on the spacer. For longer spacers, the flow field is more like a 1-D cylindrical flow field. The assumption for both geometries is that the medium is homogeneous and isotropic.
As more pore gas is removed from the spacer, the larger is the volume from which the sample is drawn in the formation. Typically, the tube volume is purged of its gas and the sample is collected thereafter.
Because the tubing is gathered in interior sleeves of the liner, it is relatively easy to emplace many sampling ports in the hole.
For conductivities of less than 0.00001cm/sec, the conductivity of the formation can be inferred from the measured flow rate in a 0.170” id tube.
For higher conductivities, the flow rate is dominated by the pressure drop in the tubing. These flow limits are determined by the diameter of the tubing, the hole diameter and the length of the tubing. For higher conductivities, a separate tube can be installed to measure the pressure in the spacer (with no flow in the pressure tube) and a second larger tube can be installed during manufacture to provide the measured flow rate into the spacer (the pressure drop in the larger tube is then unimportant). If conductivity/permeability measurements are important, the two tube geometry for each port should be discussed with FLUTe.
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