Analysts believe 50 percent of China's tap water does not meet national drinking water standards, but the problem is not so severe as to cause an immediate threat to human health.

Beijing-based Century Weekly magazine quoted insiders of related authorities as saying that an unreleased survey of the country's water quality conducted by the Ministry of Housing and Urban-Rural Development in 2009 showed that 50 percent of tap water fails to meet standards for bacteria and heavy metals.

Song Lancheng, chief engineer of the ministry's water quality supervising body, told the magazine that of the 4,000 water treatment plants surveyed, 1,000 failed to meet national standards. He was quoted as saying the quality of tap water has not improved since 2009.

Zou Ji, a professor of the School of Environment and Natural Resources at Renmin University of China, told the Global Times that the public should be concerned about the quality of water in their taps.

"Tap water undergoes many different tests, and failing a single test will cause the water to be 'disqualified,'" Zou said.

The country's 4,000 water plants produce 60 million tons of tap water daily, which is used by 400 million people.

"Polluted drinking water can harm the upper respiratory tract and cause other ailments depending on what kind of pollutant it contains," Zou said, adding that rural areas face a more serious problem as much  of the water in villages is untreated.

The magazine report also said tap water can be contaminated by outdated water treatment technologies.

Wang Hong, vice president of Elan Environmental Purification Technology, agreed that tap water may be contaminated as it travels from the treatment plant to people's homes.

"It's almost impossible that treated water would fail to meet standards, the pollution is caused during transportation since most of the pipes haven't been maintained for a long time," Wang told the Global Times.

Zou said that some factories d0 not have the financial resources to update their equipment.

New national drinking water standards, which will match European Union standards, are set to take effect this July.

Wang said the new standard will greatly improve people's quality of life and protect the interests of enterprises that specialize in water purification.

"We will see if the new standards are strictly followed by treatment plants and effectively supervised by local governments. I'm not that optimistic tap water will immediately meet the new standard, but it is moving toward this trend in bigger cities," Zou said.

Cheng Shuli contributed to this story