UGT suction probe S33 / S34 / S35 with ceramic tip, acrylic glass standpipe, valves and separate vacuum and sampling line

The suction probes S33 to S35 are equipped with an acrylic glass standpipe up to 200 cm long, into which a ceramic tip (P80; Ø20 x 50 mm) is glued tightly. The standpipe not only makes it easier to install the suction probe, but also serves as a storage volume (shaft collection) for the soil solution obtained. This means that no additional sampling vessels are required, although these can easily be connected if needed. Storing the sample in the standpipe also ensures that it remains at soil temperature to a large extent.

Three separate lines run inside the standpipe:

• A vacuum line through which negative pressure is applied in the standpipe.
• An overflow line through which the soil water flows from the suction cup into the storage volume of the standpipe.
• A sampling line is used to take the soil solution from the storage volume in the standpipe.

The suction probe head is located at the upper end of the standpipe and is equipped with valves and connectors for the overflow and sampling lines. Both lines can be closed separately using stopcocks (valves).

Both the hoses and the hose connections are made of inert PE to avoid contaminating the samples. The suction probe's well-thought-out design enables autonomous operation and prevents percolate from being sucked back into the soil during dry periods.

How it works

In the initial state, both valves on the suction probe head are closed. At the beginning of the sampling process, the valve on the lateral vacuum connection is opened, creating a vacuum in the standpipe. This vacuum ensures that soil water flows through the ceramic tip into the overflow line and then into the storage volume of the standpipe. The water remains there and cannot flow back into the soil, even if the suction tension increases due to drought.
After closing the valve at the vacuum connection, the vacuum is maintained and gradually decreases as soil water flows in. Further water inflow is not possible when the storage volume is completely filled.
The stored soil solution can be taken via the sampling line. To do this, a pump and a sampling vessel are connected to the sampling connection and a vacuum is created. After opening the sampling valve, the vacuum valve is also opened to allow air to flow in and ensure the free flow of the sample. After the sampling is complete, both valves are closed again.

The process is repeated in the same way for a new sampling.

The suction probe is suitable for operation with a permanently constant vacuum in combination with a suction probe system, as well as for a single application of vacuum. Thanks to the standardized hose connections, the suction probe is compatible with all common hand pumps, electronic pumps and vacuum control units.

Use of a groove auger during installation

For optimal installation of the suction probe in the soil, we recommend using a suitable groove auger. This tool is used to pre-drill a hole with a diameter that is slightly smaller than that of the suction probe. A diameter that is too large can favor preferential flow paths along the suction probe, causing additional water to be directed to the suction cup. This could falsify the measurement results. The appropriate pre-drill not only makes installation easier, but also ensures a proper connection between the suction probe and the surrounding soil, which ensures precise sampling.

Further general information can be found at suction probe.