The density of fresh water at a temperature of approximately 4 degrees Celsius is 1000 kg/m3.
Although the density of water varies with temperature, the density at 4degC is most commonly used because it is straightforward to remember and happens to be the temperature at which water is most dense.
The density of water is used in the calculation of pressure units which are based on the height of water columns such as meters of water (mH2O).
The density of water is used as a reference density for calculating the specific gravity of different types of liquids.
A pressure sensing device scaled in height of water pressure units can be used to measure the height of any liquid if the specific gravity is known for the specified fluid.
Hydrostatic liquid level sensor products
Borewell water level sensor for 100m water height
Hydrostatic Level Sensors
Contaminated groundwater submersible plastic body 5 psi pressure transducer & display- Dirty water, sludge & sewerage tank level 400 mbar pressure sensor