Piezometer: An Effective Measuring Tool

A piezometer is essentially a pressure-measuring device. It can either determine liquid pressure within a system by determining the height to which liquid rises against gravity or the pressure of groundwater at a determined point. It is different from a pitot tube in that it ought to measure static pressures. The very first piezometers were used in geotechnical engineering and were typically just open wells/standpipes in an aquifer. Today, there are many different types of piezometers for all kinds of applications.

The main function of a piezometer is to measure ground water levels and pore-water pressure, which yield essential information in:

• Understanding initial site conditions• Predicting the stability of slopes• Determining proper and safe rates for fill-placement• Designing systems for lateral earth pressures• Checking the quality and performance of containment systems• Evaluating the efficiency of drainage systems

Some of the most common types of piezometers available in the market today include:

• Standpipe piezometer – The most basic type of underground water pressure-measuring tool, a standpipe piezometer features a filter tip, which joins to a riser pipe extending to the surface. Water then flows through the filter and into the riser pipe. A water level indicator signifies readings. • Vibrating wire piezometer – The vibrating wire piezometer is also commonly deployed as it is suitable for many different types of applications. It can be embedded in fill, installed in a borehole, or hung in a standpipe. A data logger or a portable readout can be used to obtain readings from a vibrating wire piezometer.• Pneumatic piezometer – Different from a standpipe and vibrating wire piezometers, a pneumatic piezometer operates using gas pressure. It too, can be installed in the same places as vibrating wire piezometers, only it acquires readings using a pneumatic indicator. • Titanium piezometer – For drawdown tests, it is best to use a titanium piezometer, which is specifically designed for use with industrial data loggers.

Just like any other measuring devices, piezometers have their limitations. For instance, standpipe piezometers require direct access to the pipe's top in order to measure the water level. If you need regular and continuous access to it, using a diaphragm piezometer is recommended as this can be operated from a separate, remote readout station. Standpipes may also present occasional problems when the pipe is not installed straight or if false signals are present because of organic growth on its walls. If this is the case, it is best to consider supplementing other types of piezometers to get the most accurate results.