Water engineer Hanno van der Merwe said they were trying to pin down the source of the bacteria, however he ruled out the likeliness of the reservoirs, the newest being more than 30 years old, being the problem.
"For this specific incident, it's not impossible but very unlikely the infection came from the roofs - we only found a high count in the one reservoir." Van der Merwe said.
"It's unlikely the reservoirs were responsible, nevertheless we are continuing the work to ensure they are improved. That's required for the years to come."
Three days of testing have now produced clear results, residents have now been given the all clear to stop boiling water. However, Campbell is determined to invest in improving the older reservoirs.
"We don't want to be [boiling water] every two or three weeks, our engineers are working diligently to work out what's gone wrong - we don't think it's a water supply problem," Campbell said.
"Our testers do a pretty good job, but they're still done by man, so maybe we need to account for the 'human factor'. It's not the nicest time of year to start mucking around with people's water, but we will spend the money - we knew we would be up for $10 million to $15 million anyway, we're just bringing that forward."
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