Toilet flushing trivia #387 ...

Hong Kong uses seawater for over 80% of its toilet flushing - has done since the 1950s.

Since the late 1950's, the Water Supplies Department has supplied seawater, primarily for flushing, in government and government-aided high density development schemes, but subsequently for flushing supplies throughout the urban areas and the new towns. Nearly 80% of the population is now supplied with seawater for flushing.

The extensive use of seawater has helped to reduce the demand on fresh water for flushing. During 2007, an average of 741,000 cubic metres per day of seawater was supplied for flushing purposes, conserving an equivalent amount of potable water.

Seawater is not treated to the same standard as fresh water but its standard still has to comply with the guidelines laid down by the department to prevent objectionable characteristics. The seawater is firstly screened by strainers to remove sizeable particles. It is then disinfected with chlorine or hypochlorite before being pumped to service reservoirs and for distribution to consumers.

See - Hong Kong Water Supplies Department - Seawater for Toilet Flushing.