Council will undertake another round of targeted hydrant flushing in Blenheim to help resolve ongoing water discolouration following the introduction of chlorine to the town’s water supply network in mid-October.
“Chlorine was introduced to Blenheim’s network late last year, and we’re pleased to report that adequate chlorine residuals have been present throughout the network since around the end of December,” Treatment Operations Engineer Mike Davies said.
“However, some residents have experienced water discolouration and we want to address this as quickly and effectively as we can.”
“When chlorine enters a network for the first time, it has a cleaning effect on the inside of the pipes, dislodging naturally occurring biofilms and sediment. This is why we flushed all 1200-plus hydrants across the network before chlorination began - and that preparation helped reduce the impact,” Mr Davies said.
Since chlorination started, Council has flushed around 200 hydrants a second time in response to discolouration complaints. The yellow discolouration occurs when dissolved iron inside cast iron water pipes oxidises and forms rust particles.
While the colour is off-putting, there is no need for concern - iron in drinking water has no maximum limit under Drinking Water Quality Assurance Rules. The next phase will involve a flushing programme targeting areas of the network where older cast iron water mains are predominant.
“We will be flushing upwards of 380 hydrants in early March, which we expect to take a couple of weeks. Residents should be aware that flushing activity may cause short-term discolouration that wasn’t previously evident - but it should be short-lived,” Mr Davies said.
Discolouration complaints are continuing to be handled by Council on a case-by-case basis. Residents experiencing issues are encouraged to run their taps to flush the discolouration first, and to call Council if the problem does not clear within a reasonable timeframe.
“We understand this has been frustrating for some residents over the past few weeks. While we can’t give a definitive timeline on when discolouration issues will fully resolve, experience from Christchurch suggests the bulk of these issues should ease within the next couple of months,” Mr Davies said.
For more information go to the Blenheim water supply webpage
