b. Submerged Inlets. Submerged inlets are found on many common plumbing
fixtures and are sometimes necessary features of the fixtures if they are to function
properly. Examples of this type of design are siphon-jet urinals or water closets,
flushing rim slop sinks, and dental cuspidors. Old style bathtubs and lavatories had
supply inlets below the flood level rims, but modern design has minimized or eliminated
this hazard in new fixtures. Some submerged inlets that are difficult to control are those
that are not apparent untiI a significant change in water level occurs or where a supply
may be conveniently extended below the Iiquid surface by means of a hose or auxiIiary
piping. Any time the means have been established for a continuous flow of water
between a potable water supply and a source of contaminated water, a cross
connection has been made. This cross connection wiII convert the intended inlet to a
siphon if the pressure in the water supply is reversed. Figure 6-11 illustrates several
typical cross connections caused by the submerged inlet principle.
Figure 6-11. Typical submerged inlet type cross connections.