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Purpose: The Water FLUTe system is a multi-level water sampling and head measurement system.

The general characteristics:

• Quickly emplaced from a shipping reel by eversion into the borehole.

• Seals the entire borehole with a pressurized flexible liner of polyurethane coated Nylon fabric. The sealing pressure is provided by excess water head in the liner.

• Defines the sampling interval for each port with an exterior permeable surround called a "spacer."

• Draws the pore liquid into the central pumping system directly from the formation.

• Allows the water level for each port to be tagged from the surface and can be provided with recording pressure transducers for each port.

• Provides 1-2 gals, typically, from each port per stroke.

• All ports can be purged and sampled simultaneously.

• Is relatively easy to remove for repairs, replacement, etc…

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Water FLUTe Installation

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12 Ports in 6" Borehole to 600 ft

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Purging 12 ports simultaneously


The flexible liner is emplaced from a shipping reel. The top of the liner is attached to the surface casing (see the video and drawing, "Just Add Water") and the liner is then pushed down inside the casing a short distance. Water is added to the interior of the liner, driving the liner deeper into the hole, pulling the inside-out liner from the reel. The interior water pressure on the everting end of the liner is the driving force of the installation. Once the liner is fully extended in the hole, the geometry looks like that in the drawing below for a single port system.

The installation of a Water FLUTe is affected by the depth and diameter of the hole, the relative transmissivity of the hole, the depth to the water table, and the rate at which water can be supplied to fill the liner.

The installation procedure describes the difference when installing in a tight hole versus one that allows water to flow freely into the formation. If the hole is too tight to allow the liner to push the water into the formation, the water can be pumped from beneath the liner using a
pump tube emplaced in the hole before the liner installation.

Water FLUTe systems are usually installed in uncased boreholes. Installations into multi-screened cased holes are also common. Varying borehole diameters are accommodated from 3-30 inches. The Water FLUTe can be installed through smaller casing into larger open holes below the casing, or into "telescoped" casing. The liner is completely heat welded without the use of any glues. The tubing is usually PVDF (polyvinylidene fluoride). Other types of tubing can be used.

In most situations, the Water FLUTe installation takes less than one day.
Some installations have required less than one hour

Everting liners into boreholes

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Sample pumping system

The water flows from the formation into the spacer, through the port, into the tube which lies on the inside surface of the liner. The water flows from the port via the tube, to the bottom of the hole, and then upward through a Teflon ball check valve into the "U" shaped tube. The water rises in both legs of the U tube. In the larger (1/2"id) tube, the water level can be tagged from the surface. A gas pressure is applied to the large tube to drive the sample water through the second check valve to the surface. After purging the tubing, the sample water does not contact the drive gas. The large tube and pumping hardware are not everted into the borehole, but simply lowered as a tubing bundle following the liner to the bottom. Note that all the water in the borehole is isolated inside the liner.

The spacer, port, tubing and pump system shown are duplicated for each port. The liner is pressed against the borehole wall by the excess head in the liner above the local water table.

Pressure transducers are often attached to the sampling tubing just below the first check valve to measure the head in the formation at the port location. The transducer is upstream of the valves in the pumping system. The pressure transducer can be calibrated to the head measured in the sampling system with a tag line.

Our experience with Water FLUTe systems now spans 16 years. Water FLUTe systems have been installed in 48 states in the U.S., and many foreign countries. More detailed descriptions and publications are available at

A typical installation of a 12 port system is shown in the photos below.
This installation took about 4 hrs., including the attachment of the surface hardware. The wellhead for the 12 port system with 12 pressure transducers is shown in the bottom left photo. The bottom right photo shows the simultaneous purging of all 12 ports, which took about 5 minutes.
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Installing 12 port WaterFLUTe

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12 Ports in 6" Borehole to 600 ft

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Purging 12 ports simultaneously


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Difference from Standard Water FLUTe systems?

The Shallow Water FLUTe (SWF) is the least expensive Water FLUTe system, and, possibly the least expensive multi-level system available. The system consists of a continuous borehole liner, spacers defining the sampling intervals, and tubing directly to the surface from each sampling interval (see the drawing). The SWF depends on the ability to pump the water sample to the surface using a peristaltic pump, so the maximum water table depth at any sampling interval is < 25 ft. The SWF is shipped on a small plastic reel and hence the shipping and installation is similar to a blank FLUTe liner.
The SWF is capable of up to 10-20 ports per borehole depending on the hole diameter from 4 inches to greater. There is no need for an exterior seal with grout, sand or bentonite. The liner seals the entire hole and the water is drawn directly from the formation. The installation can be done by most customers. The water table depth at each port can be measured with a FLUTe vacuum water level meter system. A particular advantage is that the air couple transducer (ACT) system for monitoring water table levels can be used with a simple surface connection to a pressure transducer. The transducers are then located in the surface casing for easy access for reuse, replacement or repair.
A positive displacement sampling design of the same system is available at modest additional cost, but only half as many ports are available, and no ACT option.
The drawing shows an advantage of the Water FLUTe design that is also well suited for the SWF. The sampling ports can be either water sampling intervals or vadose pore gas sampling intervals. ACT pressure transducers for the vadose sampling intervals allow the monitoring of pore gas pressures.
The SWF system is fully removable for other use of the borehole or easy abandonment by grouting the borehole. The system can be used for artesian situations with a heavy mud fill. Whereas the system can be used for a variety of borehole depths, the Standard Water FLUTe system is better suited for boreholes more than 200 ft deep or for deeper water tables.
The SWF is well suited for detection of tracer arrivals in that the purge volumes are minimal and the sample is drawn directly from the formation. Because there is not an interior tubing bundle, a transparent liner version allows one to watch for the arrival of strongly dyed injections, such as potassium permanganate, using a borehole camera. That option requires a special polyester liner instead of the standard nylon liner.
A FLUTe method called a
precise gradient measurement is available in order to measure vertical gradients within ~ 1mm between any two ports in the liner.
Because there is no field assembly and no annular sealing materials needed, and the system is fully removable by inversion from the borehole, the overall cost of the Shallow Water FLUTe system is often the least expensive multi-level sampling and head measurement option of the multi-level monitoring systems. Furthermore, there is no concern about the seal of granular materials in a slender annulus.
The ability to continuously monitor water table variations with standard pressure transducers at 10-20 elevations is an exceptional high resolution capability for cross-hole conductivity assessments. Once the cross-borehole measurement is finished, the transducers can be moved to another borehole for reuse.