Bad … Chantal Snell with a sample of the water. Credit:Danielle Smith ''It tasted like Dettol and smelled like gas and made my mouth go numb until the next day,'' resident Chantal Snell said. Her neighbour held a candle to the water as it came out of his kitchen tap and watched it flare and spark when it came close to the water, which smelled like gas. Sydney Water's explanation that the problems were caused by bitumen getting into water pipes during routine maintenance has since been discredited by a number of scientists. Sydney Water has also admitted it did not test the water for gas. The affected suburbs are around the Botany Industrial Park, where the groundwater is severely contaminated from the chemical giant Orica's former ChlorAlkali plant.

Ms Snell said her neighbour alerted her that something was wrong with the water. ''After my neighbour rang I went and tried the water,'' she said. ''It tasted like Dettol and smelled like gas and made my mouth go numb until the next day. It was like a burnt feeling in my mouth. ''When I spoke to my other neighbours, some were throwing up, some had the same tingling and burning sensation, and some had upset stomachs.'' Her neighbour held a candle to gas-smelling water as it came out of his kitchen tap, and watched it flare and spark when close. It tasted like Dettol and smelled like gas.

Ms Snell took her own sample and had it analysed by an independent laboratory, which found chloroform and bromide - which could explain the numbness people reported. Chloroform is used as an industrial disinfectant but only small amounts are usually found in tap water, and Sydney Water has confirmed it does not use bromide in its processing, prompting speculation that the incident was cross-contamination. Sydney Water's explanation that the problems were caused by bitumen getting into water pipes during routine maintenance has since been discredited by a number of scientists. Sydney Water has also admitted it did not test the water for gas. ''The explanation for this incident has all the signs of looking like just a fobbing off,'' said Ian Brown, an analytical and industrial chemist from Hg Recoveries and who analysed both samples. ''If what Sydney Water claims is true, then a lot of very important procedures have failed. ''This incident is obviously the result of a series of bungles. Bitumen will not produce chloroform or bromochloro methanes, which were also seen in the test results.''

A spokeswoman for Sydney Water said a number of process improvements were being implemented and ''reinforced with relevant staff''. A former long- term employee has warned that Sydney Water's response echoes that of the cryptosporidium water crisis 15 years ago. ''This incident should be of great concern,'' said Dr Ian Wright, who is now at the University of Western Sydney. ''The question has to be asked is, what really happened here? Where are all the results from the samples that were taken? This is what happened with the cryptosporidium case, they did not share the information in an open and timely manner.'' Despite 100 complaints about the water, Sydney Water told Fairfax Media it had taken only four samples. One was from the home of Ms Snell - one of the worst affected. But Sydney Water has said its employee bungled the sample taking, and so no results were available. However it said it had made available other results to whoever wanted them.

The only official results Ms Snell has seen were from a Sydney Water sample taken the day after the pollution incident, from a house in another street. She has not been given any results from samples taken at the height of the contamination. The Greens state MP Cate Faehrmann said the agency had serious questions to answer. ''How could Sydney Water mess up taking a water sample from a resident during a contamination incident? If it wasn't deliberate then it was plain incompetence. ''Why do residents always seem to be kept in the dark about whether their water, air or soil is contaminated? Clearly laws need changing to ensure increased transparency by agencies and companies whose activities can risk human health and the environment.'' Sydney Water has denied any cover-up. A spokeswoman said: ''Once Sydney Water had determined the cause of the problem this information was conveyed to the public.''

Christopher McRae, a lecturer at Macquarie University's department of chemistry, said Sydney Water's explanation that the taste and smell was caused by substances known as PAHs which had come from the bitumen was ''somewhat silly''. Dr McRae said the low levels showing in the Sydney Water test results could not have caused such tastes or smells and the test results released ''do not in any way explain what happened''. The Sydney Water spokeswoman said they do not have an explanation for the reactions to the water but said: ''NSW Health advised that short-term exposure, including showering and drinking a glass of water, is not a risk to health.'' The affected suburbs are around the Botany Industrial Park, where the groundwater is severely contaminated from the chemical giant Orica's former ChlorAlkali plant. An Orica spokesman said that on the day of the contamination incident there was leakage from its groundwater treatment plant water recovery network due to a hole in a steel pipe. He said about 640 litres was recovered in an underground interceptor pit and then transferred to the effluent system, which is fitted with an analyser continuously monitoring for chlorinated compounds - which were not detected.

''Orica is not aware of any means by which groundwater that is captured and treated in the GTP process could enter the drinking-water supply,'' the spokesman said. Sydney Water said the water supply operates under a pressurised system that stops the entry of groundwater, and Orica's waste water and recycling pipes are not near the drinking-water supply. Do you know more? Email n.obrien@fairfaxmedia.com.au