CP1 and CP15 Standpipe Piezometer

The CP standpipe (or Casagrande) piezometer is used to measure pore-water pressure and water level in permeable soils n many geographical applications.


The CP standpipe piezometer is a filter element that is attached to a riser pipe. When installed as a piezometer, the filter is located in a sand intake zone at the location where pore-water pressure is to be monitored. A bentonite pellet or chip seal is placed over the sand intake zone and the remaining borehole is backfilled with grout.

A monitoring well installation consists of a filter-element attached to a riser, backfilled with sand to within a few meters of the ground surface. A bentonite seal at the surface prevents runoff water flowing into the monitoring well.

The CP1 consists of a porous plastic filter inside a perforated rigid PVC body. The CP15 is a crush resistant porous plastic filter. Both piezometers are used with rigid PVC riser pipes.

Water enters the riser until the water pressure inside the filter equals the water pressure in the soil. A water level indicator can be then used to measure the depth of water.

The CP15 can be used in combination with the PWS piezometer if continuous monitoring is needed.

Type Porous plastic Porous plastic
Length 350 mm 300 mm, 600 mm
Diameter 33 mm 38 mm
Fitted adaptors 3/4 Sch 40 tubing optional For rigid PVC standpipe  19 or 25 mm diameter model CP15
Filter Plastic, ~50 μm, ~10 kPa low air entry