Online Encyclopedia of Western Signs and Ideograms Symbols.com

Symbol 24:29

2421

24:29 · The sign 2420a placed within a rectangle is a modern ideogram for water catchment area, storage place for firefighting equipment and similar meanings, always in the context of fire prevention.
    Compare with 2401a, the first entry sign in this group, that is somewhat similar in structure and has been used for water, spring, or well.