In accordance with new national Drinking Water Standards, the council had to wait for three days of clear results before it could declare a return to "business as usual".
Council chief executive Monique Davidson said that the positive result came from a "false sample", which she believed could have been caused by cross-contamination picked up at the site or in the laboratory.
She said the typical response would be to treat the water, but Takapau's water supply, like all supplies in CHB, was treated to a "very high" standard through the use of chlorine and other measures.
"The fact that the water is chlorinated should be a cause for comfort [for residents]."
"The minimum requirement of chlorine concentration in potable water, as set out by the Drinking Water Standards, is 0.2 ppm [parts per million].
"At the time of sampling the chlorine concentration was 0.34ppm. at the treatment plant and 0.47ppm in the reticulation [system]."
Mrs Davidson said the HBDHB was satisfied that E.coli could not survive at those concentrations.
However, the incident would still be regarded as a transgression by the health board and treated as such, similar to when council had to issue a "boil-water" notice to residents at Porangahau and Te Paerahi on the CHB coast last March.
She said a "transgression report" about the Porangahau incident had been completed by council staff and a subsequent meeting had been held with the HBDHB, which was "satisfied that CHBDC had reacted in a responsible and satisfactory manner to ensure the safety of the potable drinking water supplies."
Backflow preventers:
To protect against potential contamination of the district's water supplies, the council will soon be contacting the owners of 148 properties in CHB, telling them they need to spend at least $2000 each to install backflow preventers.
The testable devices stop the backflowing (syphoning) of water from a source back into the council's water network.
Of those properties, the council estimates that 20 will require larger commercial devices which cost around $2500, while the other 128 will require smaller devices that cost about $2000.
The council has decided that property owners will foot the bill for installing the devices as well as an annual testing charge of $306, and pay to replace the devices at the end of their 30-year lifespan.
Mrs Davidson said the properties were spread across the district and included a number of farms, but the majority were commercial businesses.
"There is a potential risk of backflow contamination from a number of properties in the district and therefore council believes that this risk should be addressed.
"Whilst backflow prevention is not a new requirement, there is no doubt that following the Havelock North inquiry [into the 2016 gastro outbreak], there will certainly be a stronger focus on drinking water compliance requirements."
The council has yet to start contacting the property owners but Mrs Davidson wants the work to start in the "near future".
How does CHB get its drinking water?
Waipukurau: Water is drawn from three shallow bores within the Tukituki River gravels. The water is disinfected by the addition of chlorine gas to the water at the reservoir.
Waipawa and Otane: The water sources are shallow ground water bores adjacent to the Waipawa River. The water is disinfected with chlorine gas at the pump stations. Water is supplied to Otane via a dedicated pipe line from the Waipawa reservoirs.
Takapau: Water is pumped from a single bore located at the northeastern end of Meta St into tanks beside the pump station. The water has a relatively high manganese content which requires treating to remove. The water is disinfected by the addition of chlorine gas at the pump station.
Porangahau: There is only one source: a shallow bore beside the Porangahau Country Club golf course. Water is pumped from the bore to storage tanks on Old Hill Rd above the township. The water has a high iron content which requires treatment to remove. The water is disinfected by the addition of chlorine gas at the pump station.
Kairakau: There are two bores from which water is pumped to the treatment plant storage tanks, then to storage tanks located on the face of the hill at the northern end of the beach. The water is chlorinated.
Pourerere: The water source is a spring on Ouepoto Station which is tapped and the water gravity-fed to storage tanks at the camping ground. At the camp, the water is chlorinated and stored ready for use.
