WATER MANOMETER

Typical Number in Hospital: 20

Cost Bands:

References: 2

A vertical glass tube, or a U-tube makes an excellent manometer suitable for the calibration of pressure measuring apparatus, or to measure slowly changing pressures such as the central venous pressure or bladder pressure. The theory of operation is identical to the mercury manometer but there is a scale factor difference of 13.6 since water is a lighter fluid. Greater sensitivity can be achieved by inclining the tube. In this way the distance the surface of the water must move to register a particular vertical rise is greater.

Water manometers are normally calibrated in cmH2O which is convenient when using water filled tubing, since errors of level normally cancel out. Water manometers would normally be found in intensive care applications (for CVP pressure) and as calibration units wherever pressures are measured using electric manometers (theatres, high dependency wards, urodynamic clinics, cardiac catheter laboratories).