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Seawater for Flushing

Nowadays, many places in the world are still using fresh water for toilet flushing. On the other hand, the WSD has been supplying seawater for flushing in government and government-aided high density development schemes since the late 1950's. Up till now, Hong Kong is one of the few places extensively applying seawater for flushing. The use of such a sustainable resource continues to play an important role in Hong Kong’s water management. Total 270 million cubic metres of seawater is supplied every year, conserving an equivalent amount of fresh water. We will continue to extend the use of seawater for flushing to reduce fresh water demand.

Seawater Supply System Further Extended

In 2015, the WSD successfully expanded Hong Kong’s seawater supply coverage to 85% of the population. At present, seawater is available to buildings in Northwest New Territories (including Tuen Mun East, Hung Shui Kiu, Tin Shui Wai and Yuen Long Town Centre) and Pok Fu Lam for flushing. When the seawater supply system is fully implemented in the expanded zones, total 22 million cubic metres of fresh water will be conserved every year, equivalent to the full capacity of the Tai Lam Chung Reservoir.

A map showing the area with seawater supply

On the other hand, since some of the inland areas (e.g. the North District) are distant from the coast, the installation of a seawater supply system at this stage is uneconomical. Yet, we will review this issue proactively, and, whenever technically feasible and cost-effective, continue to expand our seawater supply system or exploit new water resources (e.g. reclaimed water) in order to further reduce the use of fresh water for flushing.

Quality of Seawater for Flushing

It is true that 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 WSD to ensure the quality of seawater for flushing to be acceptable. The seawater is firstly screened by strainers to remove sizeable particles, and then disinfected with chlorine or hypochlorite to ensure the water quality meets the WSD’s guideline on color, turbidity, odour, etc., before being pumped to service reservoirs and for distribution to consumers.

A TYPICAL SEA WATER SUPPLY SYSTEM (SCHEMATIC)

Consumers may consider joining our Quality Water Supply Scheme for Buildings – Flushing Water in order to enhance the hygiene and operation of their building’s flushing system. For more details please refer to the Quality Water Supply Scheme for Buildings – Flushing Water web page.

Conversion to Seawater for Flushing

Conversion to seawater for flushing not only conserves our precious fresh water resource but, owing to lower electricity consumption for supplying seawater than fresh water, reduces carbon dioxide emission. Consumers, furthermore, can reduce their water bills.

The plumbing materials used in flushing systems approved by the Water Authority (WA) since the 1960s have already been designed to be resistant to seawater corrosion. There should not be any problem with the maintenance of the inside service after conversion to seawater for flushing.

When consumers or property management agencies receive a letter issued by the WA or his delegates about conversion to seawater for flushing, they should employ licensed plumbers to inspect the inside service. If modification works are required, application to the WA is necessary. After inspection/completion of modification works by licensed plumbers, consumers or agencies should apply to the WA for connection to seawater mains. With the required connection fee paid, the WSD will schedule the works for pipe connection and seawater supply.


Conversion to Seawater for Flushing(Image)
Quality Water Supply Scheme for Buildings – Flushing Water(Image)
Wave-powered Cleaning System(Image)