A government watchdog unveiled that the level of tap water in China meeting standards stood at 83 percent, seeking to calm panic stirred by a previous report putting the rate at just 50 percent. However, this data did not quell all doubts. 

In 2009, reports showed that 41.8 percent of tap water did not meet national standards. This was reduced to 17 percent in 2011 due to an upgrading of technology and piping and the renewal of water sources, said Shao Yisheng, director of urban water quality supervision at the Ministry of Housing and Urban-Rural Development (MOHURD).

"It's disappointing the official test results came out passively after the media reports. The authority should lay them out promptly and regularly, with detailed information concerning the times and places the tests took place at," said Li Fuxing, director of Beijing Institute of Public Health and Drinking Water.

On Monday, Century Weekly magazine quoted insiders as saying that an unreleased MOHURD survey from 2009 showed that half of tap water had failed to meet bacteria and heavy metal standards.

Feng Ding, a lawyer from Nanjing wrote to the ministry on Wednesday, saying "according to regulations effective in 2007, the ministry is obliged to reveal water quality test results every year."

Wang Hao, academician at the China Institute of Water Resources and Hydropower Research, said the quality would be even lower when reaching household taps due to an outdated transportation system.

New national drinking water standards, which will match European Union standards, are set to take effect this July. Beijing Waterworks Group announced on Thursday that tap water at the citywide plants had already met all the new standards.