SINGAPORE - A four-tick rating for washing machines will be introduced while zero-tick taps and mixers will be phased out from Saturday (April 1), PUB said.

"Washing in the kitchen sink and showering are the two most water-consuming activities at home," national water agency PUB said in a statement on Friday.

Showering takes up 29 per cent of total household water usage, while dishwashing takes up 22 per cent, according to PUB. Laundry takes up about 19 per cent of domestic water usage.

One to three-tick fittings do not cost more than less efficient zero-tick models, but using a three-tick tap or mixer can save, on average, 54 per cent more water when compared to a zero-tick one, the agency said.

PUB will also introduce a four-tick rating for washing machines under the mandatory water efficiency labelling scheme.

This will complement the two and three-tick models that are currently available, PUB said.

The three-tick washing machines currently use 9 litres or less of water per kg load. With the introduction of the new rating, washing machines that use between 6 and 9 litres of water per kg load will be given a three-tick rating.

Machines that use 6 litres or less of water per kg load will be given a four-tick rating.

Based on a market survey commissioned by PUB, the market share of three-tick models has increased from 37 per cent in 2011 to 88 per cent in the first quarter of 2016.

"This is indicative of an increased consumer preference for water-efficient washing machines," PUB said.

PUB's director of water supply (network), Mr Michael Toh, said these changes are part of PUB's plan to phase out water-inefficient fittings and appliances.

"By looking out for the water efficiency label affixed on the water fittings and appliances, consumers can purchase water-efficient fittings and appliances, save water in their daily activities, and reduce their water bill," he said.

Mr Toh added: "They (consumers) can save 43 per cent of water per wash when they use a four-tick washing machine instead of a two-tick washing machine."

The mandatory water efficiency labelling scheme was introduced in 2009. The scheme covers water fittings such as taps and mixers, dual-flush low capacity flushing cisterns, urinal flush valves and waterless urinals, as well as appliances such as washing machines.

It will be extended to include dishwashers from October 2018.