Activists in the eastern city of Nanjing have called on the ruling Chinese Communist Party to make public details of drinking water quality following a clampdown on the industry last year and amid growing fears for public health and consumer safety.
China issued a document on July 1 last year setting new safety standards for public drinking water suppliers, boosting the number of mandatory purity tests to 106 from just 35, in the first update to the rules since the 1950s.
Reports at the time showed that just two Chinese cities had passed clean drinking water tests using the new measures, but activists say there has been no update from the government since.
Cheng Yuan, who heads the civil action group Nanjing Citizens Under Heaven, said the government had responded to some of its requests for information, but not all.
"Actually, the thing we really wanted to gain from this was to establish the right of the public to know what is going on," Cheng said. "We need to know if there is a problem, and if so, where the problems are."
"That's the only way we can solve them," he said.
Cheng said the group had requested in particular the detailed results of large-scale nationwide testing of domestic water supplies done by China's housing ministry in 2009.
"I heard that they produced a report, but that has never been made public," Cheng said.
Less than half fit to drink
Official media reported in January that less than 50 percent of China's piped water supply passed the government's own quality standards.
Public health experts are warning of the risk of a growing burden of disease as a result of dwindling supplies of drinkable water, as over-drilling of wells in drought-stricken northern China has led to unacceptably high levels of salt in the water table.
Water in southern China is commonly siphoned off from rivers to irrigate crops, with the run-off from farmlands pouring large quantities of nitrates and phosphorus from fertilizers back into the rivers, activists say.
Officials have warned that China is facing a "grave" environmental crisis, with more than half its cities affected by acid rain and one-sixth of its major rivers too polluted even to water the crops with.
'Serious' levels of pollution
Former photographer and Huaihe river activist Huo Daishan said tests carried out on Huaihe river water last week had shown "serious" levels of pollution.
"It's not just the Huaihe that has serious pollution levels now," Huo said. "Pollution is getting worse and worse in many other places, and some are even worse than the Huaihe."
He said there were a number of possible sources for China's drinking water.
"One source is from natural water systems, for example, a certain section of the Huaihe river, and the water quality is extremely poor," Huo said.
"It has to undergo all manner of processes and treatments ... some of which create new pollution in themselves."
"The rest comes from other sources, like groundwater and artesian wells, but the groundwater in many areas isn't up to standard, either," he said. "For example, they might have levels of fluorine or arsenic that are over the legal limit."
"All of these problems exist to varying degrees in various locations," Huo said.
Chinese consumers are reeling in the wake of a string of public health scandals affecting foodstuffs and medicines in recent years, including melamine-tainted infant formula milk, used "gutter" cooking oil, and tainted vaccines.
Campaigners say that China has an exemplary set of environmental protection legislation, but that close ties between business and officials mean that it is rarely enforced at a local level.
Worsening levels of air and water pollution, as well as disputes over the effects of heavy metals from mining and industry, have forced ordinary Chinese to become increasingly involved in environmental protection and protest, according to a 2013 report from the Friends of Nature group.
Reported by Yang Fan for RFA's Mandarin Service. Translated and written in English by Luisetta Mudie.