The Housing Authority did not do enough to ensure water safety for residents of public housing estates, a judge chairing an inquiry into contaminated drinking water at 11 estates said yesterday. Meanwhile, contractors for the estates denied any knowledge of lead-containing materials being used to connect water pipes in the homes, and blamed mistakes possibly made by workers and a lax sub-contracting system for the scandal. On the fourth day of the hearing, Mr Justice Andrew Chan Hing-wai, chairman of the commission of inquiry, asked why components used in the water supply works had not been checked when sanitary-ware such as toilet paper holders and toilet bowls had detailed checks. "You won't know whether people have cheated if you never check those pipes," Chan said. READ MORE: Hong Kong tycoon Li Ka-shing pocketed HK$40 million as sole supplier of bottled water at height of city's lead-in-pipes scandal Giving evidence yesterday, deputy director of housing Ada Fung Yin-suen said water supply works had been directly regulated by rules set out by the city's water authorities, and housing authorities were only responsible for ensuring the buildings were up to standard. Excessive lead was found in materials used to solder pipes in flats on 11 estates, prompting the government to set up the commission to investigate. According to their written statements, the main contractors said they were unaware solder containing lead had been used to connect the water supply parts when they built the flats, adding they did not buy those materials. China State Construction and Yau Lee Construction said lower-tier subcontractors or plumbers might have used the soldering materials in question without notifying them, but they could not be sure who was to blame. Shui On, another public housing builder, said workers might have bought the wrong soldering materials by mistake. Excessive lead was found in materials used to solder pipes in flats on 11 public housing estates, prompting the government to set up the commission to investigate. The inquiry will ascertain the causes of excess lead found in drinking water and make recommendations to ensure water safety. The hearings will continue into January.