这是规定。不是你说拿桶倒水就没人管了。buliding code
§145.0302 When Swimming Pool, Spa, and Hot Tub Regulations Apply
The building regulations of this division apply to any outdoor swimming
pool. An outdoor swimming pool means any structure intended for swimming or
recreational bathing that can contain water over 18 inches in depth and is
not totally contained within a residential structure and surrounded on all
four sides by walls of the structure.
This includes in-ground, aboveground and on-ground swimming pools, hot tubs,
and spas.
(Added 12-9-1997 by O-18451 N.S.; amended 12-6-1999 by O-18728 N.S.;
effective
1-1-2000.)