There was an increase in the number of citizen complaints this year regarding drinking water quality, revealing the questionable quality of secondary supply water in the city.

Statistics from the Beijing health inspection institute show there have been around 360 water complaints in 2009, 110 of which relate directly to secondary supplies of water.

Secondary water supplies refer to water providers that service communities and tall buildings, after receiving water from a primary source such as a water company.

Wei Xiangdong, in charge of water quality in the inspection institute, declined to disclose the exact number of complaints over previous years but said there was a rising trend.

"I don't think it's because the water quality is getting worse. It's just because the public is more concerned about their health," Wei said.

Residents who live on the sixth floor or above tend to use secondary supply water. Due to a lack of pressure, water is stored in rooftop tanks before being sent down through the building.

The tanks require annual cleaning and maintenance in order to ensure hygiene.

"Around 30 to 40 percent of residents are using secondary supplies of water in downtown Beijing, but our supervision and management teams are too small to cope with it all," Wei told METRO yesterday.

According to Wei, some property management companies do not do their jobs well enough. He said they don't clean water tanks and test water quality in a regular manner and this produces a heavy workload for the institute.

A building usually needs at least two thirds of the residents to agree before it can upgrade outdated piping systems.

"But some people refuse because they don't want to give money to solve the problematic water quality," Wei added.

Colin Friedman, managing director at China Expert International, says if most people in Beijing can drink the water, he can do.

Friedman, who has lived in Beijing since January 2003, said most people boil water before consuming it, but it only removes the biological problems of the water and not physical problems like rust.

"Old piping systems will cause some rust. It may not look pretty, but it's not my concern," Friedman said.