ftH2O - Feet of Water Column at 4 deg C Pressure Unit

Foot of Water Column is an American and English low value pressure unit, now used mostly in the USA where feet and inches are the standard units for measuring distance. 1 Foot of Water Column at 4 degC (39.2 degF) equals 2989.07 Pascals.

The main use for the feet of water pressure unit is to measure fluid level in a tank or depth in a liquid such as sea water. Water is the most common liquid found on Earth and the density of all other types of liquid are referenced and compared to the density of water. If the specific gravity (ratio of density comparison with water) of a certain liquid is known, it will be possible to convert the required height range into feet of water to make it possible to select the correct hydrostatic range for a liquid level measurement device.

For more background information on American and British hydrostatic pressure units please go to our inches of water page.

You will find various conversion factors for 1 foot of water gauge in the list below.

To convert other pressure units into feet of water column please click on the appropriate link in the table below.

Calculate any number of ftWG values using our online pressure converter.

View the calculation for deriving ftH2O from SI units or the list of different forms of writing ftH2O that you might see used.

inH2O Pressure Conversion Factors

0.0298907	bar
0.433528	psi
29.8907	mbar
2989.07	N/m²
2989.07	Pa
29.8907	hPa
2.98907	kPa
0.00298907	MPa
0.0304800	kg/cm²
304.800	mmH2O 4°C (39.2°F)
30.4800	cmH2O 4°C (39.2°F)
0.304800	mH2O 4°C (39.2°F)
12	inH2O 4°C (39.2°F)
1	ftH2O 4°C (39.2°F)
22.4198	mmHg 0°C (32°F)
2.24198	cmHg 0°C (32°F)
0.882671	inHg 0°C (32°F)
22.4198	Torr
22419.8	mTorr
0.0294998	atm
0.0304800	at
29890.7	dyn/cm²
6.93644	oz/in²
22419.8	µHg 0°C (32°F)
0.000193539	tsi (uk, long)
0.000216764	tsi (usa, short)
0.0312140	tsf (usa, short)
62.4280	psf
30.4800	g/cm²

Please note that the conversion factors above are accurate to 6 significant figures.

ftH2O Derivation

The calculation below shows how the pressure unit Feet of Water Column (ftH2O) is derived from SI Units.

Formula

Pressure = Force / Area
Force = Mass x Acceleration
Mass = Density x Volume
Volume = Area x Height
Acceleration = Distance / (Second x Second)

SI Units

Mass: Kilogram (kg)
Length: Metre (m)
Time: Second (s)
Force: Newton (N)
Pressure: Pascal (Pa)

Input Values

Density = Water Density at 4degC = 1000 kg/m³
Area = 1 m²
Height = 1 ft = 0.3048 m
Acceleration = Standard Gravity = 9.80665 m/s²

Calculation

1 ftH2O Mass = 1000 kg/m³ x 1 m² x 0.3048 m = 304.8 kg
1 ftH2O Force = 304.8 kg x 9.80665 m/s² = 2989.06692 N
1 ftH2O Pressure = 2989.06692 N / 1 m² = 2989.0992 Pa

inH2O Alternate Descriptions

These are the different versions used for identifying inH2O that you may find elsewhere.

Feet of H2O
Foot of H2O
Feet of Water Column
Foot of Water Column
Feet of Water Gauge
Foot of Water Gauge
ftH2O
ftWC
ftWG
ftWS
ftAq
ft H2O
ft WC
ft WG
ft WS
ft Aq
'H2O
'WC
'WG
'WS
'Aq