For Mr Teo Oon Peng's household, the replacement of their old 9-litre toilet to a more water-efficient model yesterday will help the family cut their water bill - which is about $40 a month - by 10 per cent.

"We usually try to save water by flushing our toilet with the water that we use to wash clothes and shower," said the 61-year-old minibus driver who lives with his wife and mother-in-law. While the $4 they will save is not a lot, it is "better than nothing", he said.

His family is one of 9,000 households that are expected to benefit from national water agency PUB's project to replace non-water-efficient toilets, wash basin taps and kitchen sink taps.

The three-year project was rolled out at the start of this month, with some 200 eligible households receiving letters notifying them of the replacements. About one-quarter have consented to the works.

Residents should contact PUB or its appointed contractor to arrange for works to be done. Toilet replacements should take about three hours.

All costs will be borne by PUB.

The water agency is in the process of sending letters to other eligible households in areas such as Bishan, Bukit Panjang, Choa Chu Kang and Jurong.

The project, announced in this year's Budget debate, is intended for residents on community assistance schemes and living in HDB flats built between 1986 and 1992.

The 9-litre toilets, which use twice as much water as new models, were phased out in 1992. Water-efficient models use less than 4.5 litres for a full flush and less than 3 litres for a half-flush.

PUB has also collaborated with the Singapore Plumbing Society (SPS) to offer those who are not eligible for the free service a discounted rate. The replacement of a 9-litre toilet to a more efficient one typically costs $450 in the market but HDB home owners can get it done for $250.

"Our goal is to help Singapore save more water," said Mr Amos Phua, the membership chairman of SPS, an association that represents trained and qualified plumbing practitioners.

Yesterday, Minister for the Environment and Water Resources Masagos Zulkifli visited residents in Tampines to view the replacement of their non-water-efficient toilets and taps.

Speaking to reporters, Mr Masagos said: "Saving 10 per cent of the water bill per household may not seem significant but, when accumulated, it means a lot for the water conservation efforts of the nation."