A piezometer is a small-diameter observation well used to measure the hydraulic head of groundwater. Typical configuration of piezometer consists of filter tip surrounded by sand filter zone at the bottom. Above the tilter tip is bentonite seal and bentonite-cement grout.
As piezometer is used to measure the water pressure at the tip, long response time is required.
Contrast to piezometer, standpipe is used to measure the water level directly and hence shorter response time is expected. The configuration of standpipe is similar to that of piezometer, except that the bentonite seal/ grout are replaced by sand/ gravel. Typical standpipe arrangement is as follow:
