More restaurants are putting a price on tap water, to the frustration of diners.
Around one in 10 dining establishments now charge for a glass of water, at least twice the number from just two years ago, said Restaurant Association of Singapore executive director Lim Rui Shan.
The typical price is between 30 cents and 80 cents. And the reason is rising costs.
Industry sources say an average restaurant can end up spending from $5,000 to $10,000 every year serving free water.
There is also the loss in drink sales, which can make up at least 20 per cent of a restaurant's total earnings, and the manpower cost involved in what is already a tight labour market, as service crew have to constantly refill glasses.
The Saveur Group started putting a 30-cent price tag on each refillable glass of water at two of its French restaurants and its Italian restaurant in October last year.
Company co-owner Dylan Ong said: "Operating costs have gone up by around 20 per cent to 30 per cent in general and the market is very tough. The cost of serving water for free is not justifiable in the long run.
"If you ask for ice water at a coffee shop, it costs 30 cents, so we decided on this price."
The company has received several complaints about this over the last few months. In some cases, the water is provided free, especially after the customer gets very upset.
"We do not want to go overboard," said Mr Ong, 28.
About two to three years ago, Chinese restaurant chain Crystal Jade also started charging 30 cents for boiled water and this practice is currently in place at 21 of its 25 outlets here.
Another food and beverage brand, Skinny Pizza, stopped serving plain water for free in April last year.
It now charges 50 cents for a glass of water flavoured with herbs and fruits such as mint and strawberries. A spokesman for the brand said: "Unfortunately, business costs have spiralled over the years and we have to do all we can to find a balance."
According to the Department of Statistics, there were 2,477 restaurants in 2013.
Establishments which still offer tap water for free said that there are customers who take advantage. Some come in a group, order one dish and keep asking for water refills.
Said Ms Debby Lim, 27, senior marketing executive of Peranakan Place, which runs two bars and a cafe: "What the customer sees is just a glass of water; what we see is time and effort taken to wash, pour, serve and refill.
"It would help if customers could be more understanding, too."
Still, being made to pay for water is a bugbear among diners.
Said 24-year-old undergraduate Randolph Quek: "It should be free, as it comes from the tap. It should be a basic service extended to all customers. We are already paying service charge."
Consumers here have come to expect complimentary glasses of water when they dine, and consider it a must-have for restaurants, said Ms Caroline Lim, director of the Institute of Service Excellence at Singapore Management University.
"When restaurants remove the complimentary water, we can imagine the immediate response - disappointment," she said, urging restaurants to make clear their water policy from the start - for instance, stating clearly on menus the price of a glass of tap water.