Steve Barker wrote:
Ours is in gallons. Can't imagine why they would measure water in cubic
anything. Liquids are measured in gallons.

Steve Barker

Oh ye of little faith (And a narrow outlook).
There are many units of volume used world wide.
The most common, universal and easy to use metrically around much of
the world, is litres.
US neighbour Canada officially uses litres but still 'thinks' in
gallons, but that's Imperial gallons (which are about) 20% larger than
US ones.
In North America we use so much water that even domestically measuring
in gallons is cumbersome.
So units such as those mentioned (One unit = 748 gallons etc.) are the
norm.