To encourage water conservation, national water agency PUB will phase out the sale of less efficient taps and mixers as well as introduce new ratings for washing machines.

A new "four-tick" rating will be introduced next year for washing machines under the Mandatory Water Efficiency Labelling Scheme.

The scheme enables consumers to make informed decisions by choosing more water-efficient water fittings and appliances such as taps and mixers, and flushing cisterns. The more ticks a product has, the more water-efficient it is.

Currently, washing machines sold have either two- or three-tick water efficiency ratings.

The sale and supply of taps and mixers with "zero ticks" will also be disallowed from early next year.

These measures are all part of the Government's plan to manage water demand.

Speaking in Parliament yesterday, Minister for the Environment and Water Resources Masagos Zulkifli said that extreme weather patterns due to climate change will pose a challenge to Singapore's water sustainability.

While the amount of water used by Singapore residents fell from 160 litres per person per day in 2003, to 150 litres in 2014, the figure rose last year - to about 151 litres of water a day.

Separately, Senior Minister of State for the Environment and Water Resources Amy Khor said that, by 2018, the manufacture, import and export of non-compliant mercury-added batteries will be prohibited.

This refers to those containing more than five parts-per-million mercury per cell.

Singapore generates more than 60,000 tonnes of e-waste each year, and this will only grow as electronic items become more common, Dr Khor added.

A study is under way to look at how feasible system designs can be developed for the collection, recycling and management of e-waste in Singapore.