m H₂O
meter of water column
Pressureexact by definition
The metre of water column is exactly 9806.65 pascals on the conventional basis, close to 0.1 bar. It is how pump head is stated everywhere outside North America: a pump that lifts water 30 m develops 30 m of head regardless of the fluid, which is exactly why the unit survives.
Watch out: Head in metres is a height, not a pressure, until a fluid density is supplied. A pump delivering 30 m of head produces 294 kPa on water and 400 kPa on a brine at 1.36 specific gravity. The conversion here assumes water. This is the reason pump curves are published in metres of head and not in kilopascals.
| 1 m H₂O | 9.80665 kPa |
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